497

EXPLANATORY NOTE

On behalf of the Gabelli International Small Cap Fund (the “Fund”), a series of the GAMCO Global Series Funds, Inc. (the “Corporation”), and pursuant to Rule 497(e) under the Securities Act of 1933, attached for filing is an exhibit containing interactive data format risk/return summary information. The interactive data file included as an exhibit to this filing relates to the supplement filed with the Securities and Exchange Commission on behalf of the Funds pursuant to Rule 497(e) on September 6, 2017.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Dec. 31, 2016
Registrant Name	dei_EntityRegistrantName	GAMCO GLOBAL SERIES FUNDS, INC
Central Index Key	dei_EntityCentralIndexKey	0000909504
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Sep. 06, 2017
Document Effective Date	dei_DocumentEffectiveDate	Sep. 06, 2017
Prospectus Date	rr_ProspectusDate	Apr. 28, 2017

XML

Apr. 28, 2017

GAMCO GLOBAL SERIES FUNDS, INC.

Supplement dated September 6, 2017

to

Prospectus dated April 28, 2017; and

Statement of Additional Information dated April 28, 2017

This supplement amends certain information in the Prospectus (the “Prospectus”) and Statement of Additional Information (“SAI”), each dated April 28, 2017, of GAMCO Global Series Funds, Inc. (the “Corporation”). Unless otherwise indicated, all other information included in the Prospectus and SAI, or any previous supplements thereto, that is not inconsistent with the information set forth in this supplement remains unchanged. Capitalized terms not otherwise defined in this supplement have the same meaning as in the Prospectus and SAI.

Revised Fee and Expense Waiver For Class AAA Shares of The Gabelli International Small Cap Fund

Effective September 5, 2017, Gabelli Funds, LLC, the Adviser, has agreed to amend its contractual agreement with respect to Class AAA Shares of The Gabelli International Small Cap Fund (the “Fund”) and to waive its investment advisory fees and/or to reimburse expenses of the Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00% for Class AAA shares of the Fund. This arrangement is in effect through April 30, 2018.

Under these same arrangements, the Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00% for Class AAA shares after giving effect to the repayments.

There are no changes to the terms of the contractual agreement with respect to the Fund’s Class A, C, I, or T shares or share classes of other funds in the Corporation.

The Fund’s waiver/reimbursement arrangements are in effect through April 30, 2018, and may be terminated only by the Board of Directors of the Corporation before such time.

Revised Fees and Expenses Table

To reflect the changes in the contractual fee and expense waivers, the section “Fees and Expenses” in the Corporation’s Prospectus as it relates to the Fund is modified as follows:

The Gabelli International Small Cap Fund (the “International Small Cap Fund”)

Fees and Expenses of the International Small Cap Fund:

This table describes the fees and expenses that you may pay if you buy and hold shares of the International Small Cap Fund. You may qualify for sales charge discounts on Class A shares if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Gabelli/GAMCO family of mutual funds. More information about these and other discounts is available from your financial professional and in the section entitled, “Classes of Shares” on page 37 of the prospectus and in Appendix A, “Sales Charge Reductions and Waivers Available through Certain Intermediaries,” attached to the prospectus.

	Class AAA Shares			Class A Shares			Class C Shares			Class I Shares			Class T Shares(1)
Shareholder Fees
(fees paid directly from your investment):
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)		None			5.75	%		None			None			2.50	%
Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)		None			None			1.00	%		None			None
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)		None			None			None			None			None
Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)		2.00	%		2.00	%		2.00	%		2.00	%		2.00	%
Exchange Fee		None			None			None			None			None
Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment):
Management Fees		1.00	%		1.00	%		1.00	%		1.00	%		1.00	%
Distribution and Service (Rule 12b-1) Fees		0.25	%		0.25	%		1.00	%		None			0.25	%
Other Expenses		1.55	%		1.55	%		1.55	%		1.55	%		1.55	%
Total Annual Fund Operating Expenses(2)		2.80	%		2.80	%		3.55	%		2.55	%		2.80	%
Fee Waiver and/or Expense Reimbursement(2)		(1.80	)%		(0.79	)%		(0.79	)%		(1.55	)%		(0.79	)%
Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement(2)		1.00	%		2.01	%		2.76	%		1.00	%		2.01	%

(1) Class T shares are not currently offered for sale.

(2) The Adviser has contractually agreed to waive its investment advisory fees and/or to reimburse expenses of the International Small Cap Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00%, 2.00%, 2.75%, 1.00%, and 2.00% for Class AAA, Class A, Class C, Class I, and Class T shares, respectively. Under this same arrangement, the International Small Cap Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the International Small Cap Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00%, 2.00%, 2.75%, 1.00% and 2.00%for Class AAA, Class A, Class C, Class I, and Class T shares, respectively, after giving effect to the repayments. This arrangement is in effect through April 30, 2018 and may be terminated only by the Board of Directors of the Corporation before such time. The Fund will carry forward, for a period not to exceed three years from the date that an amount is waived, any fees in excess of the expense limitation and repay the Adviser such amount provided the Fund is able to do so without exceeding the lesser of (1) the expense limit in effect at the time of the waiver or reimbursement, as applicable, or (2) the expense limit in effect at the time of recoupment.

Expense Example

This example is intended to help you compare the cost of investing in the International Small Cap Fund with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the International Small Cap 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 has a 5% return each year and that the International Small Cap Fund’s operating expenses remain the same. 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 AAA Shares	$	102	$	697	$	1,319	$	2,997
Class A Shares	$	767	$	1,323	$	1,903	$	3,469
Class C Shares	$	379	$	1,016	$	1,774	$	3,767
Class I Shares	$	102	$	645	$	1,216	$	2,769
Class T Shares	$	449	$	1,024	$	1,624	$	3,244

You would pay the following expenses if you did not redeem your shares of the International Small Cap Fund:

	1 Year		3 Years		5 Years		10 Years
Class AAA Shares	$	102	$	697	$	1,319	$	2,997
Class A Shares	$	767	$	1,323	$	1,903	$	3,469
Class C Shares	$	279	$	1,016	$	1,774	$	3,767
Class I Shares	$	102	$	645	$	1,216	$	2,769
Class T Shares	$	449	$	1,024	$	1,624	$	3,244

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

GAMCO GLOBAL SERIES FUNDS, INC

Prospectus Date

rr_ProspectusDate

Apr. 28, 2017

Supplement [Text Block]

ggsfi_SupplementTextBlock

GAMCO GLOBAL SERIES FUNDS, INC.

Supplement dated September 6, 2017

to

Prospectus dated April 28, 2017; and

Statement of Additional Information dated April 28, 2017

This supplement amends certain information in the Prospectus (the “Prospectus”) and Statement of Additional Information (“SAI”), each dated April 28, 2017, of GAMCO Global Series Funds, Inc. (the “Corporation”). Unless otherwise indicated, all other information included in the Prospectus and SAI, or any previous supplements thereto, that is not inconsistent with the information set forth in this supplement remains unchanged. Capitalized terms not otherwise defined in this supplement have the same meaning as in the Prospectus and SAI.

Revised Fee and Expense Waiver For Class AAA Shares of The Gabelli International Small Cap Fund

Effective September 5, 2017, Gabelli Funds, LLC, the Adviser, has agreed to amend its contractual agreement with respect to Class AAA Shares of The Gabelli International Small Cap Fund (the “Fund”) and to waive its investment advisory fees and/or to reimburse expenses of the Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00% for Class AAA shares of the Fund. This arrangement is in effect through April 30, 2018.

Under these same arrangements, the Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00% for Class AAA shares after giving effect to the repayments.

There are no changes to the terms of the contractual agreement with respect to the Fund’s Class A, C, I, or T shares or share classes of other funds in the Corporation.

The Fund’s waiver/reimbursement arrangements are in effect through April 30, 2018, and may be terminated only by the Board of Directors of the Corporation before such time.

Revised Fees and Expenses Table

To reflect the changes in the contractual fee and expense waivers, the section “Fees and Expenses” in the Corporation’s Prospectus as it relates to the Fund is modified as follows:

The Gabelli International Small Cap Fund (the “International Small Cap Fund”)

Fees and Expenses of the International Small Cap Fund:

This table describes the fees and expenses that you may pay if you buy and hold shares of the International Small Cap Fund. You may qualify for sales charge discounts on Class A shares if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Gabelli/GAMCO family of mutual funds. More information about these and other discounts is available from your financial professional and in the section entitled, “Classes of Shares” on page 37 of the prospectus and in Appendix A, “Sales Charge Reductions and Waivers Available through Certain Intermediaries,” attached to the prospectus.

	Class AAA Shares			Class A Shares			Class C Shares			Class I Shares			Class T Shares(1)
Shareholder Fees
(fees paid directly from your investment):
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)		None			5.75	%		None			None			2.50	%
Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)		None			None			1.00	%		None			None
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)		None			None			None			None			None
Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)		2.00	%		2.00	%		2.00	%		2.00	%		2.00	%
Exchange Fee		None			None			None			None			None
Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment):
Management Fees		1.00	%		1.00	%		1.00	%		1.00	%		1.00	%
Distribution and Service (Rule 12b-1) Fees		0.25	%		0.25	%		1.00	%		None			0.25	%
Other Expenses		1.55	%		1.55	%		1.55	%		1.55	%		1.55	%
Total Annual Fund Operating Expenses(2)		2.80	%		2.80	%		3.55	%		2.55	%		2.80	%
Fee Waiver and/or Expense Reimbursement(2)		(1.80	)%		(0.79	)%		(0.79	)%		(1.55	)%		(0.79	)%
Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement(2)		1.00	%		2.01	%		2.76	%		1.00	%		2.01	%

(1) Class T shares are not currently offered for sale.

(2) The Adviser has contractually agreed to waive its investment advisory fees and/or to reimburse expenses of the International Small Cap Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00%, 2.00%, 2.75%, 1.00%, and 2.00% for Class AAA, Class A, Class C, Class I, and Class T shares, respectively. Under this same arrangement, the International Small Cap Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the International Small Cap Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00%, 2.00%, 2.75%, 1.00% and 2.00%for Class AAA, Class A, Class C, Class I, and Class T shares, respectively, after giving effect to the repayments. This arrangement is in effect through April 30, 2018 and may be terminated only by the Board of Directors of the Corporation before such time. The Fund will carry forward, for a period not to exceed three years from the date that an amount is waived, any fees in excess of the expense limitation and repay the Adviser such amount provided the Fund is able to do so without exceeding the lesser of (1) the expense limit in effect at the time of the waiver or reimbursement, as applicable, or (2) the expense limit in effect at the time of recoupment.

Expense Example

This example is intended to help you compare the cost of investing in the International Small Cap Fund with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the International Small Cap 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 has a 5% return each year and that the International Small Cap Fund’s operating expenses remain the same. 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 AAA Shares	$	102	$	697	$	1,319	$	2,997
Class A Shares	$	767	$	1,323	$	1,903	$	3,469
Class C Shares	$	379	$	1,016	$	1,774	$	3,767
Class I Shares	$	102	$	645	$	1,216	$	2,769
Class T Shares	$	449	$	1,024	$	1,624	$	3,244

You would pay the following expenses if you did not redeem your shares of the International Small Cap Fund:

	1 Year		3 Years		5 Years		10 Years
Class AAA Shares	$	102	$	697	$	1,319	$	2,997
Class A Shares	$	767	$	1,323	$	1,903	$	3,469
Class C Shares	$	279	$	1,016	$	1,774	$	3,767
Class I Shares	$	102	$	645	$	1,216	$	2,769
Class T Shares	$	449	$	1,024	$	1,624	$	3,244

GAMCO INTERNATIONAL SMALL CAP FUND

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

ggsfi_SupplementTextBlock

GAMCO GLOBAL SERIES FUNDS, INC.

Supplement dated September 6, 2017

to

Prospectus dated April 28, 2017; and

Statement of Additional Information dated April 28, 2017

This supplement amends certain information in the Prospectus (the “Prospectus”) and Statement of Additional Information (“SAI”), each dated April 28, 2017, of GAMCO Global Series Funds, Inc. (the “Corporation”). Unless otherwise indicated, all other information included in the Prospectus and SAI, or any previous supplements thereto, that is not inconsistent with the information set forth in this supplement remains unchanged. Capitalized terms not otherwise defined in this supplement have the same meaning as in the Prospectus and SAI.

Revised Fee and Expense Waiver For Class AAA Shares of The Gabelli International Small Cap Fund

Effective September 5, 2017, Gabelli Funds, LLC, the Adviser, has agreed to amend its contractual agreement with respect to Class AAA Shares of The Gabelli International Small Cap Fund (the “Fund”) and to waive its investment advisory fees and/or to reimburse expenses of the Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00% for Class AAA shares of the Fund. This arrangement is in effect through April 30, 2018.

Under these same arrangements, the Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00% for Class AAA shares after giving effect to the repayments.

There are no changes to the terms of the contractual agreement with respect to the Fund’s Class A, C, I, or T shares or share classes of other funds in the Corporation.

The Fund’s waiver/reimbursement arrangements are in effect through April 30, 2018, and may be terminated only by the Board of Directors of the Corporation before such time.

Revised Fees and Expenses Table

To reflect the changes in the contractual fee and expense waivers, the section “Fees and Expenses” in the Corporation’s Prospectus as it relates to the Fund is modified as follows:

The Gabelli International Small Cap Fund (the “International Small Cap Fund”)

Fees and Expenses of the International Small Cap Fund:

This table describes the fees and expenses that you may pay if you buy and hold shares of the International Small Cap Fund. You may qualify for sales charge discounts on Class A shares if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Gabelli/GAMCO family of mutual funds. More information about these and other discounts is available from your financial professional and in the section entitled, “Classes of Shares” on page 37 of the prospectus and in Appendix A, “Sales Charge Reductions and Waivers Available through Certain Intermediaries,” attached to the prospectus.

	Class AAA Shares			Class A Shares			Class C Shares			Class I Shares			Class T Shares(1)
Shareholder Fees
(fees paid directly from your investment):
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)		None			5.75	%		None			None			2.50	%
Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)		None			None			1.00	%		None			None
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)		None			None			None			None			None
Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)		2.00	%		2.00	%		2.00	%		2.00	%		2.00	%
Exchange Fee		None			None			None			None			None
Annual Fund Operating Expenses
(expenses that you pay each year as a percentage of the value of your investment):
Management Fees		1.00	%		1.00	%		1.00	%		1.00	%		1.00	%
Distribution and Service (Rule 12b-1) Fees		0.25	%		0.25	%		1.00	%		None			0.25	%
Other Expenses		1.55	%		1.55	%		1.55	%		1.55	%		1.55	%
Total Annual Fund Operating Expenses(2)		2.80	%		2.80	%		3.55	%		2.55	%		2.80	%
Fee Waiver and/or Expense Reimbursement(2)		(1.80	)%		(0.79	)%		(0.79	)%		(1.55	)%		(0.79	)%
Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement(2)		1.00	%		2.01	%		2.76	%		1.00	%		2.01	%

(1) Class T shares are not currently offered for sale.

(2) The Adviser has contractually agreed to waive its investment advisory fees and/or to reimburse expenses of the International Small Cap Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00%, 2.00%, 2.75%, 1.00%, and 2.00% for Class AAA, Class A, Class C, Class I, and Class T shares, respectively. Under this same arrangement, the International Small Cap Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the International Small Cap Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00%, 2.00%, 2.75%, 1.00% and 2.00%for Class AAA, Class A, Class C, Class I, and Class T shares, respectively, after giving effect to the repayments. This arrangement is in effect through April 30, 2018 and may be terminated only by the Board of Directors of the Corporation before such time. The Fund will carry forward, for a period not to exceed three years from the date that an amount is waived, any fees in excess of the expense limitation and repay the Adviser such amount provided the Fund is able to do so without exceeding the lesser of (1) the expense limit in effect at the time of the waiver or reimbursement, as applicable, or (2) the expense limit in effect at the time of recoupment.

Expense Example

This example is intended to help you compare the cost of investing in the International Small Cap Fund with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the International Small Cap 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 has a 5% return each year and that the International Small Cap Fund’s operating expenses remain the same. 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 AAA Shares	$	102	$	697	$	1,319	$	2,997
Class A Shares	$	767	$	1,323	$	1,903	$	3,469
Class C Shares	$	379	$	1,016	$	1,774	$	3,767
Class I Shares	$	102	$	645	$	1,216	$	2,769
Class T Shares	$	449	$	1,024	$	1,624	$	3,244

You would pay the following expenses if you did not redeem your shares of the International Small Cap Fund:

	1 Year		3 Years		5 Years		10 Years
Class AAA Shares	$	102	$	697	$	1,319	$	2,997
Class A Shares	$	767	$	1,323	$	1,903	$	3,469
Class C Shares	$	279	$	1,016	$	1,774	$	3,767
Class I Shares	$	102	$	645	$	1,216	$	2,769
Class T Shares	$	449	$	1,024	$	1,624	$	3,244

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the International Small Cap Fund:

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the International Small Cap Fund. You may qualify for sales charge discounts on Class A shares if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Gabelli/GAMCO family of mutual funds. More information about these and other discounts is available from your financial professional and in the section entitled, “Classes of Shares” on page 37 of the prospectus and in Appendix A, “Sales Charge Reductions and Waivers Available through Certain Intermediaries,” attached to the prospectus.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees
(fees paid directly from your investment):

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

April 30, 2018

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts on Class A shares if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of the Gabelli/GAMCO family of mutual funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Expense Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the International Small Cap Fund with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the International Small Cap 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 has a 5% return each year and that the International Small Cap Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares of the International Small Cap Fund:

GAMCO INTERNATIONAL SMALL CAP FUND | Class AAA Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)

rr_MaximumDeferredSalesChargeOverOther

none

Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)

rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther

none

Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)

rr_RedemptionFeeOverRedemption

2.00%

Exchange Fee

rr_ExchangeFeeOverRedemption

none

Management Fees

rr_ManagementFeesOverAssets

1.00%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

1.55%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.80%

^[1]

Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(1.80%)

^[1]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

1.00%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 102

3 Years

rr_ExpenseExampleYear03

697

5 Years

rr_ExpenseExampleYear05

1,319

10 Years

rr_ExpenseExampleYear10

2,997

1 Year

rr_ExpenseExampleNoRedemptionYear01

102

3 Years

rr_ExpenseExampleNoRedemptionYear03

697

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,319

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,997

GAMCO INTERNATIONAL SMALL CAP FUND | Class A Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)

rr_MaximumDeferredSalesChargeOverOther

none

Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)

rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther

none

Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)

rr_RedemptionFeeOverRedemption

2.00%

Exchange Fee

rr_ExchangeFeeOverRedemption

none

Management Fees

rr_ManagementFeesOverAssets

1.00%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

1.55%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.80%

^[1]

Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.79%)

^[1]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

2.01%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 767

3 Years

rr_ExpenseExampleYear03

1,323

5 Years

rr_ExpenseExampleYear05

1,903

10 Years

rr_ExpenseExampleYear10

3,469

1 Year

rr_ExpenseExampleNoRedemptionYear01

767

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,323

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,903

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 3,469

GAMCO INTERNATIONAL SMALL CAP FUND | Class C Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)

rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther

none

Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)

rr_RedemptionFeeOverRedemption

2.00%

Exchange Fee

rr_ExchangeFeeOverRedemption

none

Management Fees

rr_ManagementFeesOverAssets

1.00%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

1.55%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

3.55%

^[1]

Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.79%)

^[1]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

2.76%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 379

3 Years

rr_ExpenseExampleYear03

1,016

5 Years

rr_ExpenseExampleYear05

1,774

10 Years

rr_ExpenseExampleYear10

3,767

1 Year

rr_ExpenseExampleNoRedemptionYear01

279

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,016

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,774

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 3,767

GAMCO INTERNATIONAL SMALL CAP FUND | Class I Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)

rr_MaximumDeferredSalesChargeOverOther

none

Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)

rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther

none

Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)

rr_RedemptionFeeOverRedemption

2.00%

Exchange Fee

rr_ExchangeFeeOverRedemption

none

Management Fees

rr_ManagementFeesOverAssets

1.00%

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

1.55%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.55%

^[1]

Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(1.55%)

^[1]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

1.00%

^[1]

1 Year

rr_ExpenseExampleYear01

$ 102

3 Years

rr_ExpenseExampleYear03

645

5 Years

rr_ExpenseExampleYear05

1,216

10 Years

rr_ExpenseExampleYear10

2,769

1 Year

rr_ExpenseExampleNoRedemptionYear01

102

3 Years

rr_ExpenseExampleNoRedemptionYear03

645

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,216

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,769

GAMCO INTERNATIONAL SMALL CAP FUND | Class T Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

2.50%

^[2]

Maximum Deferred Sales Charge (Load) (as a percentage of redemption price)

rr_MaximumDeferredSalesChargeOverOther

none

^[2]

Maximum Sales Charge (Load) Imposed on Reinvested Dividends (as a percentage of amount invested)

rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther

none

^[2]

Redemption Fee (as a percentage of amount redeemed for shares held 7 days or less)

rr_RedemptionFeeOverRedemption

2.00%

^[2]

Exchange Fee

rr_ExchangeFeeOverRedemption

none

^[2]

Management Fees

rr_ManagementFeesOverAssets

1.00%

^[2]

Distribution and Service (Rule 12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

^[2]

Other Expenses

rr_OtherExpensesOverAssets

1.55%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.80%

^[1],[2]

Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.79%)

^[1],[2]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

2.01%

^[1],[2]

1 Year

rr_ExpenseExampleYear01

$ 449

3 Years

rr_ExpenseExampleYear03

1,024

5 Years

rr_ExpenseExampleYear05

1,624

10 Years

rr_ExpenseExampleYear10

3,244

1 Year

rr_ExpenseExampleNoRedemptionYear01

449

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,024

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,624

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 3,244

[1] The Adviser has contractually agreed to waive its investment advisory fees and/or to reimburse expenses of the International Small Cap Fund to the extent necessary to maintain the Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement (excluding brokerage costs, acquired fund fees and expenses, interest, taxes, and extraordinary expenses) at no more than an annual rate of 1.00%, 2.00%, 2.75%, 1.00%, and 2.00% for Class AAA, Class A, Class C, Class I, and Class T shares, respectively. Under this same arrangement, the International Small Cap Fund has also agreed, during the two year period following the year of any such waiver or reimbursement by the Adviser, to repay such amount, but only to the extent the International Small Cap Fund’s adjusted Total Annual Fund Operating Expenses would not exceed an annual rate of 1.00%, 2.00%, 2.75%, 1.00% and 2.00%for Class AAA, Class A, Class C, Class I, and Class T shares, respectively, after giving effect to the repayments. This arrangement is in effect through April 30, 2018 and may be terminated only by the Board of Directors of the Corporation before such time. The Fund will carry forward, for a period not to exceed three years from the date that an amount is waived, any fees in excess of the expense limitation and repay the Adviser such amount provided the Fund is able to do so without exceeding the lesser of (1) the expense limit in effect at the time of the waiver or reimbursement, as applicable, or (2) the expense limit in effect at the time of recoupment.

[2] Class T shares are not currently offered for sale.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	GAMCO GLOBAL SERIES FUNDS, INC
Prospectus Date	rr_ProspectusDate	Apr. 28, 2017
Document Creation Date	dei_DocumentCreationDate	Sep. 06, 2017