497

COVER LETTER

November 5, 2018

Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

RE: MassMutual Select Funds

(1933 Act File No. 33-73824; 1940 Act File No. 811-8274)

Ladies and Gentlemen:

Transmitted herewith for filing by means of electronic submission on behalf of the MassMutual Select Funds pursuant to Rule 497(e) under the Securities Act of 1933, as amended, are exhibits containing interactive data format risk/return summary information that mirrors the risk/return summary information in the Prospectus for the MassMutual Select T. Rowe Price Retirement Balanced Fund, MassMutual Select T. Rowe Price Retirement 2005 Fund, MassMutual Select T. Rowe Price Retirement 2010 Fund, MassMutual Select T. Rowe Price Retirement 2015 Fund, MassMutual Select T. Rowe Price Retirement 2020 Fund, MassMutual Select T. Rowe Price Retirement 2025 Fund, MassMutual Select T. Rowe Price Retirement 2030 Fund, MassMutual Select T. Rowe Price Retirement 2035 Fund, MassMutual Select T. Rowe Price Retirement 2040 Fund, MassMutual Select T. Rowe Price Retirement 2045 Fund, MassMutual Select T. Rowe Price Retirement 2050 Fund, MassMutual Select T. Rowe Price Retirement 2055 Fund, and MassMutual Select T. Rowe Price Retirement 2060 Fund, dated February 16, 2018, as filed under Rule 497(e) on October 18, 2018. The purpose of this filing is to submit the 497(e) filing dated October 18, 2018 in XBRL for the Funds.

Please address any questions or comments to the undersigned at (860) 562-2130.

Very truly yours,

/s/Andrew M. Goldberg

Andrew M. Goldberg

Assistant Vice President and Counsel, Massachusetts Mutual Life Insurance Company

Vice President, Secretary, and Chief Legal Officer, MassMutual Select Funds

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Sep. 30, 2017
Registrant Name	dei_EntityRegistrantName	MASSMUTUAL SELECT FUNDS
Central Index Key	dei_EntityCentralIndexKey	0000916053
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Oct. 18, 2018
Document Effective Date	dei_DocumentEffectiveDate	Oct. 18, 2018
Prospectus Date	rr_ProspectusDate	Feb. 16, 2018

XML

MassMutual Select T. Rowe Price Retirement Balanced Fund

MassMutual Select T. Rowe Price Retirement Balanced Fund

MASSMUTUAL SELECT FUNDS 
MassMutual Select T. Rowe Price Retirement Funds 
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

 Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement Balanced Fund found on page 4 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement Balanced Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.39%	0.54%	0.54%	0.54%
Acquired Fund Fees and Expenses		0.39%	0.39%	0.39%	0.39%
Total Annual Fund Operating Expenses		0.78%	0.93%	1.18%	1.43%
Expense Reimbursement		(0.44%)	(0.44%)	(0.44%)	(0.44%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.34%	0.49%	0.74%	0.99%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement Balanced Fund - USD ($)	1 Year	3 Years
Class I	35	193
Class M5	50	241
Class M4	76	320
Class M3	101	398

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .34%, .49%, .74%, and .99% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement Balanced Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement Balanced Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS 
MassMutual Select T. Rowe Price Retirement Funds 
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

 Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement Balanced Fund found on page 4 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement Balanced Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.39%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.39%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.78%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.44%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.34%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 35

3 Years

rr_ExpenseExampleYear03

$ 193

MassMutual Select T. Rowe Price Retirement Balanced Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.54%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.39%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.93%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.44%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.49%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 50

3 Years

rr_ExpenseExampleYear03

$ 241

MassMutual Select T. Rowe Price Retirement Balanced Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.54%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.39%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.18%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.44%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.74%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 76

3 Years

rr_ExpenseExampleYear03

$ 320

MassMutual Select T. Rowe Price Retirement Balanced Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.54%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.39%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.43%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.44%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.99%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 101

3 Years

rr_ExpenseExampleYear03

$ 398

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .34%, .49%, .74%, and .99% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2005 Fund

MassMutual Select T. Rowe Price Retirement 2005 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2005 Fund found on page 10 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2005 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	3.20%	3.35%	3.35%	3.35%
Acquired Fund Fees and Expenses		0.41%	0.41%	0.41%	0.41%
Total Annual Fund Operating Expenses		3.61%	3.76%	4.01%	4.26%
Expense Reimbursement		(3.23%)	(3.23%)	(3.23%)	(3.23%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.38%	0.53%	0.78%	1.03%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2005 Fund - USD ($)	1 Year	3 Years
Class I	39	724
Class M5	54	769
Class M4	80	844
Class M3	105	918

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .38%, .53%, .78%, and 1.03% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2005 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2005 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2005 Fund found on page 10 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2005 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

3.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

3.61%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.23%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.38%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 39

3 Years

rr_ExpenseExampleYear03

$ 724

MassMutual Select T. Rowe Price Retirement 2005 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

3.35%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

3.76%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.23%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.53%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 54

3 Years

rr_ExpenseExampleYear03

$ 769

MassMutual Select T. Rowe Price Retirement 2005 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

3.35%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

4.01%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.23%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.78%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 80

3 Years

rr_ExpenseExampleYear03

$ 844

MassMutual Select T. Rowe Price Retirement 2005 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

3.35%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

4.26%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.23%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.03%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 105

3 Years

rr_ExpenseExampleYear03

$ 918

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .38%, .53%, .78%, and 1.03% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2010 Fund

MassMutual Select T. Rowe Price Retirement 2010 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2010 Fund found on page 18 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2010 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.23%	0.38%	0.38%	0.38%
Acquired Fund Fees and Expenses		0.41%	0.41%	0.41%	0.41%
Total Annual Fund Operating Expenses		0.64%	0.79%	1.04%	1.29%
Expense Reimbursement		(0.26%)	(0.26%)	(0.26%)	(0.26%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.38%	0.53%	0.78%	1.03%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2010 Fund - USD ($)	1 Year	3 Years
Class I	39	172
Class M5	54	219
Class M4	80	298
Class M3	105	377

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .38%, .53%, .78%, and 1.03% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2010 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2010 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2010 Fund found on page 18 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2010 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.23%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.64%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.38%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 39

3 Years

rr_ExpenseExampleYear03

$ 172

MassMutual Select T. Rowe Price Retirement 2010 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.38%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.79%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.53%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 54

3 Years

rr_ExpenseExampleYear03

$ 219

MassMutual Select T. Rowe Price Retirement 2010 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.38%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.04%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.78%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 80

3 Years

rr_ExpenseExampleYear03

$ 298

MassMutual Select T. Rowe Price Retirement 2010 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.38%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.41%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.29%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.03%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 105

3 Years

rr_ExpenseExampleYear03

$ 377

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .38%, .53%, .78%, and 1.03% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2015 Fund

MassMutual Select T. Rowe Price Retirement 2015 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2015 Fund found on page 26 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2015 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.54%	0.69%	0.69%	0.69%
Acquired Fund Fees and Expenses		0.43%	0.43%	0.43%	0.43%
Total Annual Fund Operating Expenses		0.97%	1.12%	1.37%	1.62%
Expense Reimbursement		(0.56%)	(0.56%)	(0.56%)	(0.56%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.41%	0.56%	0.81%	1.06%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2015 Fund - USD ($)	1 Year	3 Years
Class I	42	238
Class M5	57	286
Class M4	83	364
Class M3	108	442

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .41%, .56%, .81%, and 1.06% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2015 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2015 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2015 Fund found on page 26 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2015 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.54%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.43%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.97%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.56%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.41%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 42

3 Years

rr_ExpenseExampleYear03

$ 238

MassMutual Select T. Rowe Price Retirement 2015 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.69%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.43%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.12%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.56%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 57

3 Years

rr_ExpenseExampleYear03

$ 286

MassMutual Select T. Rowe Price Retirement 2015 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.69%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.43%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.37%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.56%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.81%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 83

3 Years

rr_ExpenseExampleYear03

$ 364

MassMutual Select T. Rowe Price Retirement 2015 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.69%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.43%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.62%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.56%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.06%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 108

3 Years

rr_ExpenseExampleYear03

$ 442

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .41%, .56%, .81%, and 1.06% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2020 Fund

MassMutual Select T. Rowe Price Retirement 2020 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2020 Fund found on page 34 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2020 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.05%	0.20%	0.20%	0.20%
Acquired Fund Fees and Expenses		0.46%	0.46%	0.46%	0.46%
Total Annual Fund Operating Expenses		0.51%	0.66%	0.91%	1.16%
Expense Reimbursement		(0.06%)	(0.06%)	(0.06%)	(0.06%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.45%	0.60%	0.85%	1.10%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2020 Fund - USD ($)	1 Year	3 Years
Class I	46	156
Class M5	61	204
Class M4	87	283
Class M3	112	361

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .45%, .60%, .85%, and 1.10% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2020 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2020 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2020 Fund found on page 34 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2020 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.05%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.46%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.51%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.45%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 46

3 Years

rr_ExpenseExampleYear03

$ 156

MassMutual Select T. Rowe Price Retirement 2020 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.46%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.66%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.60%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 61

3 Years

rr_ExpenseExampleYear03

$ 204

MassMutual Select T. Rowe Price Retirement 2020 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.46%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.91%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.85%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 87

3 Years

rr_ExpenseExampleYear03

$ 283

MassMutual Select T. Rowe Price Retirement 2020 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.46%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.16%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.10%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 112

3 Years

rr_ExpenseExampleYear03

$ 361

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .45%, .60%, .85%, and 1.10% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2025 Fund

MassMutual Select T. Rowe Price Retirement 2025 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2025 Fund found on page 42 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2025 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.12%	0.27%	0.27%	0.27%
Acquired Fund Fees and Expenses		0.49%	0.49%	0.49%	0.49%
Total Annual Fund Operating Expenses		0.61%	0.76%	1.01%	1.26%
Expense Reimbursement		(0.13%)	(0.13%)	(0.13%)	(0.13%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.48%	0.63%	0.88%	1.13%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2025 Fund - USD ($)	1 Year	3 Years
Class I	49	179
Class M5	64	226
Class M4	90	305
Class M3	115	383

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .48%, .63%, .88%, and 1.13% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2025 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2025 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2025 Fund found on page 42 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2025 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.12%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.61%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.48%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 49

3 Years

rr_ExpenseExampleYear03

$ 179

MassMutual Select T. Rowe Price Retirement 2025 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.27%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.76%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.63%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 64

3 Years

rr_ExpenseExampleYear03

$ 226

MassMutual Select T. Rowe Price Retirement 2025 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.27%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.01%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.88%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 90

3 Years

rr_ExpenseExampleYear03

$ 305

MassMutual Select T. Rowe Price Retirement 2025 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.27%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.26%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.13%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 115

3 Years

rr_ExpenseExampleYear03

$ 383

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .48%, .63%, .88%, and 1.13% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2030 Fund

MassMutual Select T. Rowe Price Retirement 2030 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2030 Fund found on page 50 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2030 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.04%	0.19%	0.19%	0.19%
Acquired Fund Fees and Expenses		0.52%	0.52%	0.52%	0.52%
Total Annual Fund Operating Expenses		0.56%	0.71%	0.96%	1.21%
Expense Reimbursement		(0.05%)	(0.05%)	(0.05%)	(0.05%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.51%	0.66%	0.91%	1.16%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2030 Fund - USD ($)	1 Year	3 Years
Class I	52	173
Class M5	67	221
Class M4	93	300
Class M3	118	378

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .51%, .66%, .91%, and 1.16% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2030 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2030 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2030 Fund found on page 50 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2030 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.04%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.52%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.56%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.51%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 52

3 Years

rr_ExpenseExampleYear03

$ 173

MassMutual Select T. Rowe Price Retirement 2030 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.19%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.52%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.71%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.66%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 67

3 Years

rr_ExpenseExampleYear03

$ 221

MassMutual Select T. Rowe Price Retirement 2030 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.19%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.52%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.96%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.91%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 93

3 Years

rr_ExpenseExampleYear03

$ 300

MassMutual Select T. Rowe Price Retirement 2030 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.19%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.52%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.21%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.16%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 118

3 Years

rr_ExpenseExampleYear03

$ 378

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .51%, .66%, .91%, and 1.16% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2035 Fund

MassMutual Select T. Rowe Price Retirement 2035 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2035 Fund found on page 58 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2035 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.14%	0.29%	0.29%	0.29%
Acquired Fund Fees and Expenses		0.54%	0.54%	0.54%	0.54%
Total Annual Fund Operating Expenses		0.68%	0.83%	1.08%	1.33%
Expense Reimbursement		(0.14%)	(0.14%)	(0.14%)	(0.14%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.54%	0.69%	0.94%	1.19%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2035 Fund - USD ($)	1 Year	3 Years
Class I	55	200
Class M5	70	247
Class M4	96	326
Class M3	121	404

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .54%, .69%, .94%, and 1.19% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

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Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2035 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2035 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2035 Fund found on page 58 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2035 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.14%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.54%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.68%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.54%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 55

3 Years

rr_ExpenseExampleYear03

$ 200

MassMutual Select T. Rowe Price Retirement 2035 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.29%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.54%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.83%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.69%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 70

3 Years

rr_ExpenseExampleYear03

$ 247

MassMutual Select T. Rowe Price Retirement 2035 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.29%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.54%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.08%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.94%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 96

3 Years

rr_ExpenseExampleYear03

$ 326

MassMutual Select T. Rowe Price Retirement 2035 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.29%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.54%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.33%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.19%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 121

3 Years

rr_ExpenseExampleYear03

$ 404

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .54%, .69%, .94%, and 1.19% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2040 Fund

MassMutual Select T. Rowe Price Retirement 2040 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2040 Fund found on page 66 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2040 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.05%	0.20%	0.20%	0.20%
Acquired Fund Fees and Expenses		0.56%	0.56%	0.56%	0.56%
Total Annual Fund Operating Expenses		0.61%	0.76%	1.01%	1.26%
Expense Reimbursement		(0.05%)	(0.05%)	(0.05%)	(0.05%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.56%	0.71%	0.96%	1.21%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2040 Fund - USD ($)	1 Year	3 Years
Class I	57	189
Class M5	73	237
Class M4	98	315
Class M3	123	393

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2040 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2040 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2040 Fund found on page 66 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2040 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.05%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.56%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.61%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 57

3 Years

rr_ExpenseExampleYear03

$ 189

MassMutual Select T. Rowe Price Retirement 2040 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.56%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.76%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.71%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 73

3 Years

rr_ExpenseExampleYear03

$ 237

MassMutual Select T. Rowe Price Retirement 2040 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.56%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.01%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.96%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

$ 315

MassMutual Select T. Rowe Price Retirement 2040 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.20%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.56%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.26%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.21%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 123

3 Years

rr_ExpenseExampleYear03

$ 393

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2045 Fund

MassMutual Select T. Rowe Price Retirement 2045 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2045 Fund found on page 74 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2045 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.17%	0.32%	0.32%	0.32%
Acquired Fund Fees and Expenses		0.57%	0.57%	0.57%	0.57%
Total Annual Fund Operating Expenses		0.74%	0.89%	1.14%	1.39%
Expense Reimbursement		(0.18%)	(0.18%)	(0.18%)	(0.18%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.56%	0.71%	0.96%	1.21%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2045 Fund - USD ($)	1 Year	3 Years
Class I	57	214
Class M5	73	261
Class M4	98	340
Class M3	123	418

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2045 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2045 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2045 Fund found on page 74 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2045 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.17%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.74%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 57

3 Years

rr_ExpenseExampleYear03

$ 214

MassMutual Select T. Rowe Price Retirement 2045 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.32%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.89%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.71%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 73

3 Years

rr_ExpenseExampleYear03

$ 261

MassMutual Select T. Rowe Price Retirement 2045 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.32%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.14%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.96%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

$ 340

MassMutual Select T. Rowe Price Retirement 2045 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.32%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.39%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.21%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 123

3 Years

rr_ExpenseExampleYear03

$ 418

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2050 Fund

MassMutual Select T. Rowe Price Retirement 2050 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2050 Fund found on page 82 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2050 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.09%	0.24%	0.24%	0.24%
Acquired Fund Fees and Expenses		0.57%	0.57%	0.57%	0.57%
Total Annual Fund Operating Expenses		0.66%	0.81%	1.06%	1.31%
Expense Reimbursement		(0.10%)	(0.10%)	(0.10%)	(0.10%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.56%	0.71%	0.96%	1.21%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2050 Fund - USD ($)	1 Year	3 Years
Class I	57	199
Class M5	73	246
Class M4	98	325
Class M3	123	403

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2050 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2050 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2050 Fund found on page 82 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2050 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.09%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.66%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 57

3 Years

rr_ExpenseExampleYear03

$ 199

MassMutual Select T. Rowe Price Retirement 2050 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.24%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.81%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.71%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 73

3 Years

rr_ExpenseExampleYear03

$ 246

MassMutual Select T. Rowe Price Retirement 2050 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.24%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.06%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.96%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

$ 325

MassMutual Select T. Rowe Price Retirement 2050 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.24%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.31%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.21%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 123

3 Years

rr_ExpenseExampleYear03

$ 403

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2055 Fund

MassMutual Select T. Rowe Price Retirement 2055 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2055 Fund found on page 90 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2055 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	0.35%	0.50%	0.50%	0.50%
Acquired Fund Fees and Expenses		0.57%	0.57%	0.57%	0.57%
Total Annual Fund Operating Expenses		0.92%	1.07%	1.32%	1.57%
Expense Reimbursement		(0.36%)	(0.36%)	(0.36%)	(0.36%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.56%	0.71%	0.96%	1.21%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2055 Fund - USD ($)	1 Year	3 Years
Class I	57	248
Class M5	73	295
Class M4	98	373
Class M3	123	451

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2055 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2055 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2055 Fund found on page 90 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

MassMutual Select T. Rowe Price Retirement 2055 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.35%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.92%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.36%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 57

3 Years

rr_ExpenseExampleYear03

$ 248

MassMutual Select T. Rowe Price Retirement 2055 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.50%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.07%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.36%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.71%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 73

3 Years

rr_ExpenseExampleYear03

$ 295

MassMutual Select T. Rowe Price Retirement 2055 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.50%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.32%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.36%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.96%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

$ 373

MassMutual Select T. Rowe Price Retirement 2055 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.50%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.57%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.36%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.21%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 123

3 Years

rr_ExpenseExampleYear03

$ 451

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

MassMutual Select T. Rowe Price Retirement 2060 Fund

MassMutual Select T. Rowe Price Retirement 2060 Fund

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2060 Fund found on page 98 of the Prospectus in the section titled Annual Fund Operating Expenses:

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - MassMutual Select T. Rowe Price Retirement 2060 Fund		Class I	Class M5	Class M4	Class M3
Management Fees		none	none	none	none
Distribution and Service (Rule 12b-1) Fees		none	none	0.25%	0.50%
Other Expenses	[1]	6.88%	7.03%	7.03%	7.03%
Acquired Fund Fees and Expenses		0.57%	0.57%	0.57%	0.57%
Total Annual Fund Operating Expenses		7.45%	7.60%	7.85%	8.10%
Expense Reimbursement		(6.89%)	(6.89%)	(6.89%)	(6.89%)
Total Annual Fund Operating Expenses after Expense Reimbursement	[2]	0.56%	0.71%	0.96%	1.21%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - MassMutual Select T. Rowe Price Retirement 2060 Fund - USD ($)	1 Year	3 Years
Class I	57	1,416
Class M5	73	1,458
Class M4	98	1,528
Class M3	123	1,597

                          PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Feb. 16, 2018

MassMutual Select T. Rowe Price Retirement 2060 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

MassMutual Select T. Rowe Price Retirement 2060 Fund

Supplement [Text Block]

mmsf_SupplementTextBlock

MASSMUTUAL SELECT FUNDS
MassMutual Select T. Rowe Price Retirement Funds
Supplement dated October 18, 2018 to the 
Prospectus dated February 16, 2018

This supplement provides new and additional information beyond that contained in the Prospectus and any previous supplements. It should be retained and read in conjunction with the Prospectus and any previous supplements.

Effective immediately, the following information replaces the information for the MassMutual Select T. Rowe Price Retirement 2060 Fund found on page 98 of the Prospectus in the section titled Annual Fund Operating Expenses:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

January 31, 2020

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. It assumes that you invest $10,000 in each share class of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment earns a 5% return each year and that the Fund’s operating expenses are exactly as described in the preceding table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Supplement Closing [Text Block]

mmsf_SupplementClosingTextBlock

                          PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

MassMutual Select T. Rowe Price Retirement 2060 Fund | Class I

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

6.88%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

7.45%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(6.89%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 57

3 Years

rr_ExpenseExampleYear03

$ 1,416

MassMutual Select T. Rowe Price Retirement 2060 Fund | Class M5

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

7.03%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

7.60%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(6.89%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.71%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 73

3 Years

rr_ExpenseExampleYear03

$ 1,458

MassMutual Select T. Rowe Price Retirement 2060 Fund | Class M4

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

7.03%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

7.85%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(6.89%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

0.96%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 98

3 Years

rr_ExpenseExampleYear03

$ 1,528

MassMutual Select T. Rowe Price Retirement 2060 Fund | Class M3

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

none

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

7.03%

^[1]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

8.10%

Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(6.89%)

Total Annual Fund Operating Expenses after Expense Reimbursement

rr_NetExpensesOverAssets

1.21%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 123

3 Years

rr_ExpenseExampleYear03

$ 1,597

[1] Other Expenses are based on estimated amounts for the current fiscal year of the Fund.

[2] The expenses in the above table reflect a written agreement by MML Advisers to cap the fees and expenses of the Fund (other than extraordinary litigation and legal expenses, interest expense, short sale dividend and loan expense, or other non-recurring or unusual expenses such as organizational expenses and shareholder meeting expenses) through January 31, 2020, to the extent that Total Annual Fund Operating Expenses after Expense Reimbursement would otherwise exceed .56%, .71%, .96%, and 1.21% for Classes I, M5, M4, and M3, respectively. The Total Annual Fund Operating Expenses after Expense Reimbursement shown in the above table may exceed these amounts, because, as noted in the previous sentence, certain fees and expenses are excluded from the cap. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MML Advisers.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	MASSMUTUAL SELECT FUNDS
Prospectus Date	rr_ProspectusDate	Feb. 16, 2018
Document Creation Date	dei_DocumentCreationDate	Oct. 18, 2018