497

COVER LETTER

October 3, 2012

Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

RE: MassMutual Select Funds (the “Trust”)

(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 MassMutual Select Funds pursuant to Rule 497(e) under the Securities Act of 1933, as amended (the “Securities Act”), are exhibits containing interactive data format risk/return summary information that mirrors the risk/return summary information in the Prospectus for the MassMutual Select Large Cap Value Fund, MassMutual Select Mid-Cap Value Fund, and MassMutual Select Small Cap Growth Equity Fund dated April 2, 2012, as filed under Rule 497(e) on September 17, 2012. The purpose of this filing is to submit the 497(e) filing dated September 17, 2012 in XBRL for the Funds.

Please address any questions or comments to the undersigned at (413) 744-7218.

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

MASSMUTUAL SELECT FUNDS

Supplement dated September 17, 2012 to the

Prospectus dated April 2, 2012

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 September 11, 2012, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”) replaced Davis Selected Advisers, L.P. (“Davis”) as co-subadvisers to the Large Cap Value Fund.

Effective September 12, 2012, Timberline Asset Management LLC (“Timberline”) was added as a co-subadviser to the Small Cap Growth Equity Fund.

Effective September 11, 2012, the following information replaces similar information for the Large Cap Value Fund found on page 40 in the section titled Fees and Expenses of the Fund:

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

	Class S			Class Y			Class L			Class A			Class N
Management Fees		.65%			.65%			.65%			.65%			.65%
Distribution and Service (Rule 12b-1) Fees		None			None			None			.25%			.50%
Other Expenses		.12%			.21%			.36%			.36%			.41%	(1)
Total Annual Fund Operating Expenses		.77%			.86%			1.01%			1.26%			1.56%
Fee Waiver		(.02%	)		(.02%	)		(.02%	)		(.02%	)		(.02%	)
Total Annual Fund Operating Expenses after Fee Waiver(2)		.75%			.84%			.99%			1.24%			1.54%

⁽¹⁾  Other Expenses for Class N have been restated to reflect current fees.

⁽²⁾  The expenses in the above table reflect a written agreement by MassMutual to waive .02% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

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. For Class A shares, the example includes the initial sales charge. 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:

	1 Year		3 Years		5 Years		10 Years
Class S	$	77	$	243	$	425	$	951
Class Y	$	86	$	271	$	474	$	1,058
Class L	$	101	$	319	$	555	$	1,233
Class A	$	694	$	949	$	1,224	$	2,008
Class N	$	257	$	490	$	847	$	1,854

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Class N	$	157	$	490	$	847	$	1,854

Effective September 11, 2012, the following information replaces the information found under Principal Investment Strategies on pages 40-41 for the Large Cap Value Fund.

The Fund invests primarily in large-capitalization companies that the Fund’s subadvisers, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”), believe are undervalued. Under normal circumstances, the Fund will invest at least 80% of its net assets in common stocks of companies with market capitalizations at the time of purchase of at least $5 billion. The Fund has the flexibility to invest in companies of any size and invest in non-equity securities. While most assets typically will be invested in equity securities of U.S. companies, the Fund may invest up to 20% of its total assets in foreign securities and American Depositary Receipts (“ADRs”), including emerging market securities. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stock, rights, and warrants. The Fund may at times invest a substantial portion of its assets in obligations of issuers in one or more market, economic, or industry sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

The Fund may use equity-linked notes, a type of derivative, for hedging purposes, to earn additional income, or as a substitute for direct investments. Use of equity-linked notes by the Fund may create investment leverage.

In pursuit of the Fund’s objectives, Columbia Management chooses investments by applying quantitative screens to determine yield potential. Columbia Management conducts fundamental research on, and seeks to purchase potentially attractive securities based on, its analysis of various factors, which may include current yield, dividend growth capability and history, balance sheet strength, earnings per share and free cash flow sustainability and dividend payout ratio, as well as other, statistical measures. Preference is generally given to higher dividend paying companies. Columbia Management typically uses the S&P 500^® Index for dividend yield comparison purposes.

In evaluating whether to sell a security, Columbia Management considers, among other factors, whether there is deterioration in value of the business relative to market price, or a more attractive opportunity has been identified.

Huber Capital Management employs a value investing style, investing in stocks which, in Huber Capital Management’s opinion, trade at a significant discount to the present value of future cash flows. Huber Capital Management attempts to identify out-of-favor stocks that represent solid fundamental value. Huber Capital Management identifies these investment opportunities by employing a disciplined, bottom-up investment process that emphasizes internally generated fundamental research. The process includes an initial review, in-depth analysis, and employment of Huber Capital Management’s proprietary valuation methodology.

Huber Capital Management’s decision to sell portfolio securities is based on valuation, risk, and portfolio guidelines. As individual stocks approach their intrinsic value or established target price and decline in their relative attractiveness, they become candidates for sale. Other sell decisions may occur because of deterioration in the fundamentals that supported the initial investment. Proceeds from sales are reinvested in companies that are more attractively valued based on the purchase disciplines.

Effective September 11, 2012, the following information supplements the information found under Principal Risks on pages 41-42 for the Large Cap Value Fund:

Derivatives Risk Derivatives involve risks different from, and potentially greater than, direct investments, including risks of imperfect correlation between the value of derivatives and underlying assets, counterparty default, potential losses that partially or completely offset gains, and illiquidity. Derivatives can create investment leverage and be highly volatile. Derivatives may result in losses greater than the amount invested. Many derivatives are traded in the over-the-counter market and not on exchanges.

Effective September 11, 2012, the following information supplements the information for the Large Cap Value Fund found on page 42 in the section titled Performance Information:

Going forward, the Fund’s performance benchmark index will be the Russell 1000^® Value Index rather than the S&P 500 Index because the Russell 1000 Value Index more closely represents the Fund’s new investment strategy.

The following information replaces the information found in the second paragraph under Principal Investment Strategies on page 73 for the Mid-Cap Value Fund.

The Fund is managed by two subadvisers, NFJ Investment Group LLC (“NFJ”) and Systematic Financial Management, L.P. (“Systematic”), each being responsible for a portion of the portfolio, but not necessarily equally weighted. NFJ uses a value investing style focusing on companies whose stocks the portfolio managers believe have low valuations. The portfolio managers classify the Fund selection universe by industry and then identify what they believe to be undervalued stocks in each industry to determine potential holdings for the Fund representing a broad range of industry groups. The portfolio managers then use quantitative factors to screen the Fund’s initial selection. To further narrow the universe, the portfolio managers analyze factors such as price momentum (i.e., changes in stock price relative to changes in overall market prices), earnings estimate revisions (i.e., changes in analysts’ earnings per share estimates), and fundamental changes. In selecting securities for the Fund, Systematic utilizes a two-prong, bottom-up investment strategy that unifies quantitative screening and fundamental research. Systematic’s security selection process generally favors companies with attractive valuation and positive earnings dynamics, and may consider, among other things, a company’s financial characteristics, market position, industry position, and management.

Effective September 12, 2012, the following information replaces similar information for the Small Cap Growth Equity Fund found on page 88 in the section titled Fees and Expenses of the Fund:

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

	Class Z			Class S			Class Y			Class L			Class A			Class N
Management Fees		.82%			.82%			.82%			.82%			.82%			.82%
Distribution and Service (Rule 12b-1) Fees		None			None			None			None			.25%			.50%
Other Expenses		.10%			.20%			.34%			.49%			.49%			.54%
Total Annual Fund Operating Expenses		.92%			1.02%			1.16%			1.31%			1.56%			1.86%
Fee Waiver		(.07%	)		(.07%	)		(.07%	)		(.07%	)		(.07%	)		(.07%	)
Total Annual Fund Operating Expenses after Fee Waiver(1)		.85%			.95%			1.09%			1.24%			1.49%			1.79%

⁽¹⁾  The expenses in the above table reflect a written agreement by MassMutual to waive .07% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

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. For Class A shares, the example includes the initial sales charge. 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:

	1 Year		3 Years		5 Years		10 Years
Class Z	$	87	$	283	$	499	$	1,121
Class S	$	97	$	314	$	553	$	1,238
Class Y	$	111	$	358	$	628	$	1,399
Class L	$	126	$	405	$	708	$	1,570
Class A	$	718	$	1,029	$	1,367	$	2,316
Class N	$	282	$	574	$	996	$	2,171

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Class N	$	182	$	574	$	996	$	2,171

Effective September 12, 2012, the following information replaces the information found in the first sentence of the second paragraph under Principal Investment Strategies on page 89 for the Small Cap Growth Equity Fund:

The Fund is managed by three subadvisers, Wellington Management Company, LLP (“Wellington Management”), Waddell & Reed Investment Management Company (“Waddell & Reed”), and Timberline Asset Management LLC (“Timberline”), each being responsible for a portion of the portfolio, but not necessarily equally weighted.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

MASSMUTUAL SELECT FUNDS

Prospectus Date

rr_ProspectusDate

Apr. 02, 2012

Supplement [Text Block]

mmsf2_SupplementTextBlock

MASSMUTUAL SELECT FUNDS

Supplement dated September 17, 2012 to the

Prospectus dated April 2, 2012

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 September 11, 2012, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”) replaced Davis Selected Advisers, L.P. (“Davis”) as co-subadvisers to the Large Cap Value Fund.

Effective September 12, 2012, Timberline Asset Management LLC (“Timberline”) was added as a co-subadviser to the Small Cap Growth Equity Fund.

Effective September 11, 2012, the following information replaces similar information for the Large Cap Value Fund found on page 40 in the section titled Fees and Expenses of the Fund:

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

	Class S			Class Y			Class L			Class A			Class N
Management Fees		.65%			.65%			.65%			.65%			.65%
Distribution and Service (Rule 12b-1) Fees		None			None			None			.25%			.50%
Other Expenses		.12%			.21%			.36%			.36%			.41%	(1)
Total Annual Fund Operating Expenses		.77%			.86%			1.01%			1.26%			1.56%
Fee Waiver		(.02%	)		(.02%	)		(.02%	)		(.02%	)		(.02%	)
Total Annual Fund Operating Expenses after Fee Waiver(2)		.75%			.84%			.99%			1.24%			1.54%

⁽¹⁾  Other Expenses for Class N have been restated to reflect current fees.

⁽²⁾  The expenses in the above table reflect a written agreement by MassMutual to waive .02% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

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. For Class A shares, the example includes the initial sales charge. 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:

	1 Year		3 Years		5 Years		10 Years
Class S	$	77	$	243	$	425	$	951
Class Y	$	86	$	271	$	474	$	1,058
Class L	$	101	$	319	$	555	$	1,233
Class A	$	694	$	949	$	1,224	$	2,008
Class N	$	257	$	490	$	847	$	1,854

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Class N	$	157	$	490	$	847	$	1,854

Effective September 11, 2012, the following information replaces the information found under Principal Investment Strategies on pages 40-41 for the Large Cap Value Fund.

The Fund invests primarily in large-capitalization companies that the Fund’s subadvisers, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”), believe are undervalued. Under normal circumstances, the Fund will invest at least 80% of its net assets in common stocks of companies with market capitalizations at the time of purchase of at least $5 billion. The Fund has the flexibility to invest in companies of any size and invest in non-equity securities. While most assets typically will be invested in equity securities of U.S. companies, the Fund may invest up to 20% of its total assets in foreign securities and American Depositary Receipts (“ADRs”), including emerging market securities. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stock, rights, and warrants. The Fund may at times invest a substantial portion of its assets in obligations of issuers in one or more market, economic, or industry sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

The Fund may use equity-linked notes, a type of derivative, for hedging purposes, to earn additional income, or as a substitute for direct investments. Use of equity-linked notes by the Fund may create investment leverage.

In pursuit of the Fund’s objectives, Columbia Management chooses investments by applying quantitative screens to determine yield potential. Columbia Management conducts fundamental research on, and seeks to purchase potentially attractive securities based on, its analysis of various factors, which may include current yield, dividend growth capability and history, balance sheet strength, earnings per share and free cash flow sustainability and dividend payout ratio, as well as other, statistical measures. Preference is generally given to higher dividend paying companies. Columbia Management typically uses the S&P 500^® Index for dividend yield comparison purposes.

In evaluating whether to sell a security, Columbia Management considers, among other factors, whether there is deterioration in value of the business relative to market price, or a more attractive opportunity has been identified.

Huber Capital Management employs a value investing style, investing in stocks which, in Huber Capital Management’s opinion, trade at a significant discount to the present value of future cash flows. Huber Capital Management attempts to identify out-of-favor stocks that represent solid fundamental value. Huber Capital Management identifies these investment opportunities by employing a disciplined, bottom-up investment process that emphasizes internally generated fundamental research. The process includes an initial review, in-depth analysis, and employment of Huber Capital Management’s proprietary valuation methodology.

Huber Capital Management’s decision to sell portfolio securities is based on valuation, risk, and portfolio guidelines. As individual stocks approach their intrinsic value or established target price and decline in their relative attractiveness, they become candidates for sale. Other sell decisions may occur because of deterioration in the fundamentals that supported the initial investment. Proceeds from sales are reinvested in companies that are more attractively valued based on the purchase disciplines.

Effective September 11, 2012, the following information supplements the information found under Principal Risks on pages 41-42 for the Large Cap Value Fund:

Derivatives Risk Derivatives involve risks different from, and potentially greater than, direct investments, including risks of imperfect correlation between the value of derivatives and underlying assets, counterparty default, potential losses that partially or completely offset gains, and illiquidity. Derivatives can create investment leverage and be highly volatile. Derivatives may result in losses greater than the amount invested. Many derivatives are traded in the over-the-counter market and not on exchanges.

Effective September 11, 2012, the following information supplements the information for the Large Cap Value Fund found on page 42 in the section titled Performance Information:

Going forward, the Fund’s performance benchmark index will be the Russell 1000^® Value Index rather than the S&P 500 Index because the Russell 1000 Value Index more closely represents the Fund’s new investment strategy.

The following information replaces the information found in the second paragraph under Principal Investment Strategies on page 73 for the Mid-Cap Value Fund.

The Fund is managed by two subadvisers, NFJ Investment Group LLC (“NFJ”) and Systematic Financial Management, L.P. (“Systematic”), each being responsible for a portion of the portfolio, but not necessarily equally weighted. NFJ uses a value investing style focusing on companies whose stocks the portfolio managers believe have low valuations. The portfolio managers classify the Fund selection universe by industry and then identify what they believe to be undervalued stocks in each industry to determine potential holdings for the Fund representing a broad range of industry groups. The portfolio managers then use quantitative factors to screen the Fund’s initial selection. To further narrow the universe, the portfolio managers analyze factors such as price momentum (i.e., changes in stock price relative to changes in overall market prices), earnings estimate revisions (i.e., changes in analysts’ earnings per share estimates), and fundamental changes. In selecting securities for the Fund, Systematic utilizes a two-prong, bottom-up investment strategy that unifies quantitative screening and fundamental research. Systematic’s security selection process generally favors companies with attractive valuation and positive earnings dynamics, and may consider, among other things, a company’s financial characteristics, market position, industry position, and management.

Effective September 12, 2012, the following information replaces similar information for the Small Cap Growth Equity Fund found on page 88 in the section titled Fees and Expenses of the Fund:

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

	Class Z			Class S			Class Y			Class L			Class A			Class N
Management Fees		.82%			.82%			.82%			.82%			.82%			.82%
Distribution and Service (Rule 12b-1) Fees		None			None			None			None			.25%			.50%
Other Expenses		.10%			.20%			.34%			.49%			.49%			.54%
Total Annual Fund Operating Expenses		.92%			1.02%			1.16%			1.31%			1.56%			1.86%
Fee Waiver		(.07%	)		(.07%	)		(.07%	)		(.07%	)		(.07%	)		(.07%	)
Total Annual Fund Operating Expenses after Fee Waiver(1)		.85%			.95%			1.09%			1.24%			1.49%			1.79%

⁽¹⁾  The expenses in the above table reflect a written agreement by MassMutual to waive .07% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

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. For Class A shares, the example includes the initial sales charge. 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:

	1 Year		3 Years		5 Years		10 Years
Class Z	$	87	$	283	$	499	$	1,121
Class S	$	97	$	314	$	553	$	1,238
Class Y	$	111	$	358	$	628	$	1,399
Class L	$	126	$	405	$	708	$	1,570
Class A	$	718	$	1,029	$	1,367	$	2,316
Class N	$	282	$	574	$	996	$	2,171

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Class N	$	182	$	574	$	996	$	2,171

Effective September 12, 2012, the following information replaces the information found in the first sentence of the second paragraph under Principal Investment Strategies on page 89 for the Small Cap Growth Equity Fund:

The Fund is managed by three subadvisers, Wellington Management Company, LLP (“Wellington Management”), Waddell & Reed Investment Management Company (“Waddell & Reed”), and Timberline Asset Management LLC (“Timberline”), each being responsible for a portion of the portfolio, but not necessarily equally weighted.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

MassMutual Select Large Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

mmsf2_SupplementTextBlock

MASSMUTUAL SELECT FUNDS

Supplement dated September 17, 2012 to the

Prospectus dated April 2, 2012

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 September 11, 2012, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”) replaced Davis Selected Advisers, L.P. (“Davis”) as co-subadvisers to the Large Cap Value Fund.

Effective September 11, 2012, the following information replaces similar information for the Large Cap Value Fund found on page 40 in the section titled Fees and Expenses of the Fund:

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

	Class S			Class Y			Class L			Class A			Class N
Management Fees		.65%			.65%			.65%			.65%			.65%
Distribution and Service (Rule 12b-1) Fees		None			None			None			.25%			.50%
Other Expenses		.12%			.21%			.36%			.36%			.41%	(1)
Total Annual Fund Operating Expenses		.77%			.86%			1.01%			1.26%			1.56%
Fee Waiver		(.02%	)		(.02%	)		(.02%	)		(.02%	)		(.02%	)
Total Annual Fund Operating Expenses after Fee Waiver(2)		.75%			.84%			.99%			1.24%			1.54%

⁽¹⁾  Other Expenses for Class N have been restated to reflect current fees.

⁽²⁾  The expenses in the above table reflect a written agreement by MassMutual to waive .02% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

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. For Class A shares, the example includes the initial sales charge. 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:

	1 Year		3 Years		5 Years		10 Years
Class S	$	77	$	243	$	425	$	951
Class Y	$	86	$	271	$	474	$	1,058
Class L	$	101	$	319	$	555	$	1,233
Class A	$	694	$	949	$	1,224	$	2,008
Class N	$	257	$	490	$	847	$	1,854

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Class N	$	157	$	490	$	847	$	1,854

Effective September 11, 2012, the following information replaces the information found under Principal Investment Strategies on pages 40-41 for the Large Cap Value Fund.

The Fund invests primarily in large-capitalization companies that the Fund’s subadvisers, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”), believe are undervalued. Under normal circumstances, the Fund will invest at least 80% of its net assets in common stocks of companies with market capitalizations at the time of purchase of at least $5 billion. The Fund has the flexibility to invest in companies of any size and invest in non-equity securities. While most assets typically will be invested in equity securities of U.S. companies, the Fund may invest up to 20% of its total assets in foreign securities and American Depositary Receipts (“ADRs”), including emerging market securities. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stock, rights, and warrants. The Fund may at times invest a substantial portion of its assets in obligations of issuers in one or more market, economic, or industry sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

The Fund may use equity-linked notes, a type of derivative, for hedging purposes, to earn additional income, or as a substitute for direct investments. Use of equity-linked notes by the Fund may create investment leverage.

In pursuit of the Fund’s objectives, Columbia Management chooses investments by applying quantitative screens to determine yield potential. Columbia Management conducts fundamental research on, and seeks to purchase potentially attractive securities based on, its analysis of various factors, which may include current yield, dividend growth capability and history, balance sheet strength, earnings per share and free cash flow sustainability and dividend payout ratio, as well as other, statistical measures. Preference is generally given to higher dividend paying companies. Columbia Management typically uses the S&P 500^® Index for dividend yield comparison purposes.

In evaluating whether to sell a security, Columbia Management considers, among other factors, whether there is deterioration in value of the business relative to market price, or a more attractive opportunity has been identified.

Huber Capital Management employs a value investing style, investing in stocks which, in Huber Capital Management’s opinion, trade at a significant discount to the present value of future cash flows. Huber Capital Management attempts to identify out-of-favor stocks that represent solid fundamental value. Huber Capital Management identifies these investment opportunities by employing a disciplined, bottom-up investment process that emphasizes internally generated fundamental research. The process includes an initial review, in-depth analysis, and employment of Huber Capital Management’s proprietary valuation methodology.

Huber Capital Management’s decision to sell portfolio securities is based on valuation, risk, and portfolio guidelines. As individual stocks approach their intrinsic value or established target price and decline in their relative attractiveness, they become candidates for sale. Other sell decisions may occur because of deterioration in the fundamentals that supported the initial investment. Proceeds from sales are reinvested in companies that are more attractively valued based on the purchase disciplines.

Effective September 11, 2012, the following information supplements the information found under Principal Risks on pages 41-42 for the Large Cap Value Fund:

Derivatives Risk Derivatives involve risks different from, and potentially greater than, direct investments, including risks of imperfect correlation between the value of derivatives and underlying assets, counterparty default, potential losses that partially or completely offset gains, and illiquidity. Derivatives can create investment leverage and be highly volatile. Derivatives may result in losses greater than the amount invested. Many derivatives are traded in the over-the-counter market and not on exchanges.

Effective September 11, 2012, the following information supplements the information for the Large Cap Value Fund found on page 42 in the section titled Performance Information:

Going forward, the Fund’s performance benchmark index will be the Russell 1000^® Value Index rather than the S&P 500 Index because the Russell 1000 Value Index more closely represents the Fund’s new investment strategy.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

March 31, 2014

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

Other Expenses for Class N have been restated to reflect current fees.

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. For Class A shares, the example includes the initial sales charge. 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, No Redemption Narrative [Text Block]

rr_ExpenseExampleNoRedemptionNarrativeTextBlock

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests primarily in large-capitalization companies that the Fund’s subadvisers, Columbia Management Investment Advisers, LLC (“Columbia Management”) and Huber Capital Management, LLC (“Huber Capital Management”), believe are undervalued. Under normal circumstances, the Fund will invest at least 80% of its net assets in common stocks of companies with market capitalizations at the time of purchase of at least $5 billion. The Fund has the flexibility to invest in companies of any size and invest in non-equity securities. While most assets typically will be invested in equity securities of U.S. companies, the Fund may invest up to 20% of its total assets in foreign securities and American Depositary Receipts (“ADRs”), including emerging market securities. Equity securities may include common stocks, preferred stocks, securities convertible into common or preferred stock, rights, and warrants. The Fund may at times invest a substantial portion of its assets in obligations of issuers in one or more market, economic, or industry sectors. The Fund may hold a portion of its assets in cash or cash equivalents.

The Fund may use equity-linked notes, a type of derivative, for hedging purposes, to earn additional income, or as a substitute for direct investments. Use of equity-linked notes by the Fund may create investment leverage.

In pursuit of the Fund’s objectives, Columbia Management chooses investments by applying quantitative screens to determine yield potential. Columbia Management conducts fundamental research on, and seeks to purchase potentially attractive securities based on, its analysis of various factors, which may include current yield, dividend growth capability and history, balance sheet strength, earnings per share and free cash flow sustainability and dividend payout ratio, as well as other, statistical measures. Preference is generally given to higher dividend paying companies. Columbia Management typically uses the S&P 500^® Index for dividend yield comparison purposes.

In evaluating whether to sell a security, Columbia Management considers, among other factors, whether there is deterioration in value of the business relative to market price, or a more attractive opportunity has been identified.

Huber Capital Management employs a value investing style, investing in stocks which, in Huber Capital Management’s opinion, trade at a significant discount to the present value of future cash flows. Huber Capital Management attempts to identify out-of-favor stocks that represent solid fundamental value. Huber Capital Management identifies these investment opportunities by employing a disciplined, bottom-up investment process that emphasizes internally generated fundamental research. The process includes an initial review, in-depth analysis, and employment of Huber Capital Management’s proprietary valuation methodology.

Huber Capital Management’s decision to sell portfolio securities is based on valuation, risk, and portfolio guidelines. As individual stocks approach their intrinsic value or established target price and decline in their relative attractiveness, they become candidates for sale. Other sell decisions may occur because of deterioration in the fundamentals that supported the initial investment. Proceeds from sales are reinvested in companies that are more attractively valued based on the purchase disciplines.

MassMutual Select Large Cap Value Fund | Class S

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.65%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.12%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.77%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

0.75%

^[1]

1 Year

rr_ExpenseExampleYear01

77

3 Years

rr_ExpenseExampleYear03

243

5 Years

rr_ExpenseExampleYear05

425

10 Years

rr_ExpenseExampleYear10

951

MassMutual Select Large Cap Value Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.65%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.21%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.86%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

0.84%

^[1]

1 Year

rr_ExpenseExampleYear01

86

3 Years

rr_ExpenseExampleYear03

271

5 Years

rr_ExpenseExampleYear05

474

10 Years

rr_ExpenseExampleYear10

1,058

MassMutual Select Large Cap Value Fund | Class L

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.65%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.36%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.01%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

0.99%

^[1]

1 Year

rr_ExpenseExampleYear01

101

3 Years

rr_ExpenseExampleYear03

319

5 Years

rr_ExpenseExampleYear05

555

10 Years

rr_ExpenseExampleYear10

1,233

MassMutual Select Large Cap Value Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.65%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.36%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.26%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

1.24%

^[1]

1 Year

rr_ExpenseExampleYear01

694

3 Years

rr_ExpenseExampleYear03

949

5 Years

rr_ExpenseExampleYear05

1,224

10 Years

rr_ExpenseExampleYear10

2,008

MassMutual Select Large Cap Value Fund | Class N

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.65%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.41%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.56%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

1.54%

^[1]

1 Year

rr_ExpenseExampleYear01

257

3 Years

rr_ExpenseExampleYear03

490

5 Years

rr_ExpenseExampleYear05

847

10 Years

rr_ExpenseExampleYear10

1,854

1 Year

rr_ExpenseExampleNoRedemptionYear01

157

3 Years

rr_ExpenseExampleNoRedemptionYear03

490

5 Years

rr_ExpenseExampleNoRedemptionYear05

847

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,854

MassMutual Select Mid-Cap Value Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

mmsf2_SupplementTextBlock

MASSMUTUAL SELECT FUNDS

Supplement dated September 17, 2012 to the

Prospectus dated April 2, 2012

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.

The following information replaces the information found in the second paragraph under Principal Investment Strategies on page 73 for the Mid-Cap Value Fund.

The Fund is managed by two subadvisers, NFJ Investment Group LLC (“NFJ”) and Systematic Financial Management, L.P. (“Systematic”), each being responsible for a portion of the portfolio, but not necessarily equally weighted. NFJ uses a value investing style focusing on companies whose stocks the portfolio managers believe have low valuations. The portfolio managers classify the Fund selection universe by industry and then identify what they believe to be undervalued stocks in each industry to determine potential holdings for the Fund representing a broad range of industry groups. The portfolio managers then use quantitative factors to screen the Fund’s initial selection. To further narrow the universe, the portfolio managers analyze factors such as price momentum (i.e., changes in stock price relative to changes in overall market prices), earnings estimate revisions (i.e., changes in analysts’ earnings per share estimates), and fundamental changes. In selecting securities for the Fund, Systematic utilizes a two-prong, bottom-up investment strategy that unifies quantitative screening and fundamental research. Systematic’s security selection process generally favors companies with attractive valuation and positive earnings dynamics, and may consider, among other things, a company’s financial characteristics, market position, industry position, and management.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

MassMutual Select Small Cap Growth Equity Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

mmsf2_SupplementTextBlock

MASSMUTUAL SELECT FUNDS

Supplement dated September 17, 2012 to the

Prospectus dated April 2, 2012

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 September 12, 2012, Timberline Asset Management LLC (“Timberline”) was added as a co-subadviser to the Small Cap Growth Equity Fund.

Effective September 12, 2012, the following information replaces similar information for the Small Cap Growth Equity Fund found on page 88 in the section titled Fees and Expenses of the Fund:

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

	Class Z			Class S			Class Y			Class L			Class A			Class N
Management Fees		.82%			.82%			.82%			.82%			.82%			.82%
Distribution and Service (Rule 12b-1) Fees		None			None			None			None			.25%			.50%
Other Expenses		.10%			.20%			.34%			.49%			.49%			.54%
Total Annual Fund Operating Expenses		.92%			1.02%			1.16%			1.31%			1.56%			1.86%
Fee Waiver		(.07%	)		(.07%	)		(.07%	)		(.07%	)		(.07%	)		(.07%	)
Total Annual Fund Operating Expenses after Fee Waiver(1)		.85%			.95%			1.09%			1.24%			1.49%			1.79%

⁽¹⁾  The expenses in the above table reflect a written agreement by MassMutual to waive .07% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

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. For Class A shares, the example includes the initial sales charge. 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:

	1 Year		3 Years		5 Years		10 Years
Class Z	$	87	$	283	$	499	$	1,121
Class S	$	97	$	314	$	553	$	1,238
Class Y	$	111	$	358	$	628	$	1,399
Class L	$	126	$	405	$	708	$	1,570
Class A	$	718	$	1,029	$	1,367	$	2,316
Class N	$	282	$	574	$	996	$	2,171

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

	1 Year		3 Years		5 Years		10 Years
Class N	$	182	$	574	$	996	$	2,171

Effective September 12, 2012, the following information replaces the information found in the first sentence of the second paragraph under Principal Investment Strategies on page 89 for the Small Cap Growth Equity Fund:

The Fund is managed by three subadvisers, Wellington Management Company, LLP (“Wellington Management”), Waddell & Reed Investment Management Company (“Waddell & Reed”), and Timberline Asset Management LLC (“Timberline”), each being responsible for a portion of the portfolio, but not necessarily equally weighted.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

March 31, 2014

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. For Class A shares, the example includes the initial sales charge. 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, No Redemption Narrative [Text Block]

rr_ExpenseExampleNoRedemptionNarrativeTextBlock

Except for Class N shares, the figures shown above would be the same whether you sold your shares at the end of a period or kept them. For Class N shares, you would pay the following expenses if you did not redeem your shares:

MassMutual Select Small Cap Growth Equity Fund | Class Z

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.82%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.10%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.92%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

0.85%

^[3]

1 Year

rr_ExpenseExampleYear01

87

3 Years

rr_ExpenseExampleYear03

283

5 Years

rr_ExpenseExampleYear05

499

10 Years

rr_ExpenseExampleYear10

1,121

MassMutual Select Small Cap Growth Equity Fund | Class S

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.82%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.20%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.02%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

0.95%

^[3]

1 Year

rr_ExpenseExampleYear01

97

3 Years

rr_ExpenseExampleYear03

314

5 Years

rr_ExpenseExampleYear05

553

10 Years

rr_ExpenseExampleYear10

1,238

MassMutual Select Small Cap Growth Equity Fund | Class Y

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.82%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.34%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.16%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

1.09%

^[3]

1 Year

rr_ExpenseExampleYear01

111

3 Years

rr_ExpenseExampleYear03

358

5 Years

rr_ExpenseExampleYear05

628

10 Years

rr_ExpenseExampleYear10

1,399

MassMutual Select Small Cap Growth Equity Fund | Class L

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.82%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.31%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

1.24%

^[3]

1 Year

rr_ExpenseExampleYear01

126

3 Years

rr_ExpenseExampleYear03

405

5 Years

rr_ExpenseExampleYear05

708

10 Years

rr_ExpenseExampleYear10

1,570

MassMutual Select Small Cap Growth Equity Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.82%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.49%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.56%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

1.49%

^[3]

1 Year

rr_ExpenseExampleYear01

718

3 Years

rr_ExpenseExampleYear03

1,029

5 Years

rr_ExpenseExampleYear05

1,367

10 Years

rr_ExpenseExampleYear10

2,316

MassMutual Select Small Cap Growth Equity Fund | Class N

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.82%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.54%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.86%

Fee Waiver

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

Total Annual Fund Operating Expenses after Fee Waiver

rr_NetExpensesOverAssets

1.79%

^[3]

1 Year

rr_ExpenseExampleYear01

282

3 Years

rr_ExpenseExampleYear03

574

5 Years

rr_ExpenseExampleYear05

996

10 Years

rr_ExpenseExampleYear10

2,171

1 Year

rr_ExpenseExampleNoRedemptionYear01

182

3 Years

rr_ExpenseExampleNoRedemptionYear03

574

5 Years

rr_ExpenseExampleNoRedemptionYear05

996

10 Years

rr_ExpenseExampleNoRedemptionYear10

2,171

[1] The expenses in the above table reflect a written agreement by MassMutual to waive .02% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

[2] Other Expenses for Class N have been restated to reflect current fees.

[3] The expenses in the above table reflect a written agreement by MassMutual to waive .07% of the management fees of the Fund through March 31, 2014. The agreement can only be terminated by mutual consent of the Board of Trustees on behalf of the Fund and MassMutual.

XML

Document and Entity Information	12 Months Ended
	Apr. 02, 2012
Risk/Return:
Document Type	Other
Document Period End Date	Dec. 31, 2011
Registrant Name	MASSMUTUAL SELECT FUNDS
Central Index Key	0000916053
Amendment Flag	false
Document Creation Date	Sep. 17, 2012
Document Effective Date	Sep. 17, 2012
Prospectus Date	Apr. 02, 2012

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	MASSMUTUAL SELECT FUNDS
Prospectus Date	rr_ProspectusDate	Apr. 02, 2012
Document Creation Date	dei_DocumentCreationDate	Sep. 17, 2012