Gamco Mathers Fund N-CSR Certified annual shareholder report (management investment company)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT

INVESTMENT COMPANIES

Investment Company Act file number             811-01311            

                                     The GAMCO Mathers Fund                                     

(Exact name of registrant as specified in charter)

One Corporate Center

                                         Rye, New York 10580-1422                                        

(Address of principal executive offices) (Zip code)

Bruce N. Alpert

Gabelli Funds, LLC

One Corporate Center

                                         Rye, New York 10580-1422                                        

(Name and address of agent for service)

Registrant’s telephone number, including area code:   1-800-422-3554  

Date of fiscal year end: December 31  

Date of reporting period: December 31, 2012  

Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1). The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-CSR unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 100 F Street, NE, Washington, DC 20549. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. § 3507.

Item 1. Reports to Stockholders.

The Report to Shareholders is attached herewith.

GAMCO Mathers Fund	Henry G. Van der Eb, CFA Portfolio Manager
Annual Report — December 31, 2012

To Our Shareholders,

The GAMCO Mathers Fund total return for the year ended December 31, 2012 was (6.60)% versus 16.00% for the S&P 500 Index.

Enclosed are the schedule of investments and financial statements as of December 31, 2012.

Performance Discussion (Unaudited)

At year end, the gross equity exposure was 33.64% (longs plus shorts), comprised of 0.00% long and 33.64% in short positions, with a 33.64% net short exposure (longs minus shorts). The remainder of the portfolio, as has been the case for an extended time period, was invested in short-term U.S. Treasury bills and U.S. Treasury collateralized repurchase agreements. The fixed income portfolio segment had a positive return for the year. There were no merger arbitrage portfolio positions during the year and the long and short stock segments had negative returns. Near zero percent yields on short-term U.S. Treasury bills during the year, due to the U.S. Fed’s ongoing zero percent interest rate policy, disadvantaged the overall performance of the Fund.

The Fund’s gross and net equity exposures may vary significantly from day to day in an effort to control portfolio volatility under changing market conditions. Accordingly, the quarter-end figures may not be indicative of the range of gross and net equity exposures that precede or follow each reporting period.

Since the SEC’s portfolio turnover formula excludes fixed income securities with maturities of less than one year and short sale activity from its denominator, the Fund’s turnover rate may appear very high, which can be misleading. This was the case in 2012. The Fund’s U.S. Treasury bill position was a very high proportion of assets and had a maturity of less than one year, while the average month end dollar value of long stock positions (the denominator) was negligible. Long positions were held for short time periods.

Sincerely yours,

Bruce N. Alpert

Executive Vice President

February 22, 2013

GROWTH OF A $10,000 INVESTMENT IN GAMCO MATHERS FUND (Log Scale)

Percent Average Annual Total Returns through December 31, 2012*

	1 YR			5 YRS			10 YRS			47 YRS †
GAMCO MATHERS		(6.60	)		(3.11	)		(1.12	)	7.78
Standard & Poor’s 500		16.00			1.66			7.10		9.94

The current expense ratio is 2.59% .    † From commencement of investment operations on August 19, 1965.

* Average annual total returns reflect changes in share price and reinvestment of dividends and are net of expenses. Returns represent past performance and do not guarantee future results. Investment returns and the principal value of an investment will fluctuate. When shares are redeemed they may be worth more or less than their original cost. Current performance may be lower or higher than the performance data presented. Please visit www.gabelli.com to obtain performance information as of the most recent month end. The Standard & Poor’s 500 Index is an unmanaged indicator of stock market performance. Investors should carefully consider the investment objectives, risks, charges, and expenses of the Fund before investing. The prospectus contains more information about these and other matters and should be read carefully before investing. You cannot invest directly in an index.

2

GAMCO Mathers Fund
Disclosure of Fund Expenses (Unaudited)
For the Six Month Period from July 1, 2012 through December 31, 2012	Expense Table

We believe it is important for you to understand the impact of fees and expenses regarding your investment. All mutual funds have operating expenses. As a shareholder of a fund, you incur ongoing costs, which include costs for portfolio management, administrative services, and shareholder reports (like this one), among others. Operating expenses, which are deducted from a fund’s gross income, directly reduce the investment return of a fund. When a fund’s expenses are expressed as a percentage of its average net assets, this figure is known as the expense ratio. The following examples are intended to help you understand the ongoing costs (in dollars) of investing in your Fund and to compare these costs with those of other mutual funds. The examples are based on an investment of $1,000 made at the beginning of the period shown and held for the entire period.

The Expense Table below illustrates your Fund’s costs in two ways:

Actual Fund Return: This section provides information about actual account values and actual expenses. You may use this section to help you to estimate the actual expenses that you paid over the period after any fee waivers and expense reimbursements. The “Ending Account Value” shown is derived from the Fund’s actual return during the past six months, and the “Expenses Paid During Period” shows the dollar amount that would have been paid by an investor who started with $1,000 in the Fund. You may use this information, together with the amount you invested, to estimate the expenses that you paid over the period.

To do so, simply divide your account value by $1,000 (for example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number given for your Fund under the heading “Expenses Paid During Period” to estimate the expenses you paid during this period.

Hypothetical 5% Return: This section provides information about hypothetical account values and

hypothetical expenses based on the Fund’s actual expense ratio. It assumes a hypothetical annualized return of 5% before expenses during the period shown. In this case – because the hypothetical return used is not the Fund’s actual return – the results do not apply to your investment and you cannot use the hypothetical account value and expense to estimate the actual ending account balance or expenses you paid for the period. This example is useful in making comparisons of the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in shareholder reports of other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs such as sales charges (loads), redemption fees, or exchange fees, if any, which are described in the Prospectus. If these costs were applied to your account, your costs would be higher. Therefore, the 5% hypothetical return is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. The “Annualized Expense Ratio” represents the actual expenses for the last six months and may be different from the expense ratio in the Financial Highlights which is for the year ended December 31, 2012.

	Beginning Account Value 07/01/12		Ending Account Value 12/31/12		Annualized Expense Ratio			Expenses Paid During Period*
GAMCO Mathers Fund
Actual Fund Return
		$1,000.00		$   969.60		3.49	%		$17.28
Hypothetical 5% Return
		$1,000.00		$1,007.59		3.49	%		$17.61

* Expenses are equal to the Fund’s annualized expense ratio for the last six months multiplied by the average account value over the period, multiplied by the number of days in the most recent fiscal half year (184 days), then divided by 366.

3

Summary of Portfolio Holdings (Unaudited)

The following table presents portfolio holdings as a percent of net assets as of December 31, 2012:

GAMCO Mathers Fund – Long Positions
U.S. Government Obligations	99.0	%
Repurchase Agreements	2.0	%
Other Assets and Liabilities (Net)	32.5	%

GAMCO Mathers Fund – Short Positions
Exchange Traded Funds	(25.9	)%
Retail	(4.3	)%
Commercial Services	(2.1	)%
Consumer Products	(1.2	)%
	100.0	%

The Fund files a complete schedule of portfolio holdings with the Securities and Exchange Commission (the “SEC”) for the first and third quarters of each fiscal year on Form N-Q. Shareholders may obtain this information at www.gabelli.com or by calling the Fund at 800-GABELLI (800-422-3554).The Fund’s Form N-Q is available on the SEC’s website at www.sec.gov and may also be reviewed and copied at the SEC’s Public Reference Room in Washington, DC. Information on the operation of the Public Reference Room may be obtained by calling 800-SEC-0330.

Proxy Voting

The Fund files Form N-PX with its complete proxy voting record for the twelve months ended June 30, no later than August 31 of each year. A description of the Fund’s proxy voting policies, procedures, and how the Fund voted proxies relating to portfolio securities is available without charge, upon request, by (i) calling 800-GABELLI (800-422-3554); (ii) writing to The Gabelli Funds at One Corporate Center, Rye, NY 10580-1422; or (iii) visiting the SEC’s website at www.sec.gov.

We have separated the portfolio manager’s commentary from the financial statements and investment portfolio due to corporate governance regulations stipulated by the Sarbanes-Oxley Act of 2002. We have done this to ensure that the content of the portfolio manager’s commentary is unrestricted. The financial statements and investment portfolio are mailed separately from the commentary. Both the commentary and the financial statements, including the portfolio of investments, will be available on our website at www.gabelli.com

4

GAMCO Mathers Fund

Schedule of Investments — December 31, 2012

Principal Amount			Cost		Market Value
		SHORT-TERM OBLIGATIONS — 101.0%
		Repurchase Agreements — 2.0%
	$     409,439	State Street Bank & Trust Co., 0.010%, dated 12/31/12, due 01/02/13, proceeds at maturity, $409, 439( a)		$     409,439		$     409,439
		U.S. Treasury Bills — 99.0%
	20,600,000	U.S. Treasury Bills
		0.061%†, 01/03/13(b)		20,599,931		20,599,931
		TOTAL SHORT-TERM OBLIGATIONS		21,009,370		21,009,370
		TOTAL INVESTMENTS — 101.0%		$21,009,370		21,009,370
		SECURITIES SOLD SHORT — (33.5)%
		(Proceeds received $6,869,412)				(6,969,902	)
		Other Assets and Liabilities (Net) — 32.5%				6,769,725
		NET ASSETS — 100.0%				$20,809,193

Shares			Proceeds		Market Value
		SECURITIES SOLD SHORT — (33.5)%
		Commercial Services — (2.1)%
	7,000	Morningstar Inc.		$     440,906		$     439,810
		Consumer Products — (1.2)%
	5,000	Harley-Davidson Inc.		233,450		244,200
		Exchange Traded Funds — (25.9)%
	35,000	Financial Select Sector SPDR Fund		559,370		574,000
	4,000	iShares MSCI Brazil Index Fund		208,586		224,240
	10,000	iShares MSCI Emerging Markets Index Fund		413,262		443,500
	8,000	iShares Russell 2000 Index Fund		655,899		674,542
	8,000	Powershares QQQ Trust Series 1		530,489		520,880
	4,500	SPDR Dow Jones Industrial Average ETF Trust		599,597		589,050
	4,500	SPDR S&P 500 ETF Trust		646,831		640,845
	3,500	SPDR S&P MidCap 400 ETF Trust		630,211		649,985
	14,000	Vanguard FTSE All-World Ex-US ETF		604,776		640,500
	6,000	Vanguard Total Stock Market ETF		442,885		439,740
				5,291,906		5,397,282
		Retail — (4.3)%
	5,000	McDonald’s Corp.		436,646		441,050
	3,000	Starbucks Corp.		154,601		160,860
	5,000	Tiffany & Co.		311,903		286,700
				903,150		888,610
		TOTAL SECURITIES SOLD SHORT(c)		$6,869,412		$6,969,902

(a) Collateralized by $315,000 U.S. Treasury Bond, 4.500%, due 02/15/36, market value $421,509.

(b) At December 31, 2012, $5,000,000 of the principal amount was pledged as collateral for securities sold short.

(c) At December 31, 2012, these proceeds are being held at Pershing LLC.

† Represents annualized yield at date of purchase.

See accompanying notes to financial statements.

5

GAMCO Mathers Fund

Statement of Assets and Liabilities

December 31, 2012

Assets:
Investments, at value (cost $20,599,931)	$	20,599,931
Repurchase agreements, at value (cost $409,439)		409,439
Deposit at brokers (including proceeds from securities sold short $6,869,412)		6,738,864
Receivable for Fund shares sold		128,700
Prepaid expenses		19,125
Total Assets		27,896,059
Liabilities:
Securities sold short, at value		6,969,902
Payable for Fund shares redeemed		33,656
Payable for investment advisory fees		17,458
Payable for distribution fees		4,365
Dividends payable on securities sold short		15,214
Other accrued expenses		46,271
Total Liabilities		7,086,866
Net Assets (applicable to 2,332,998 shares outstanding)	$	20,809,193
Net Assets Consist of:
Paid-in capital	$	23,568,439
Accumulated net realized loss on investments and securities sold short		(2,658,756	)
Net unrealized depreciation on securities sold short		(100,490	)
Net Assets	$	20,809,193
Shares of Beneficial Interest, each at $0.001 par value; unlimited number of shares authorized:
Net Asset Value, offering, and redemption price per share ($20,809,193 ÷ 2,332,998 shares outstanding)	$	8.92

Statement of Operations

For the Year Ended December 31, 2012

Investment Income:
Interest	$	12,834
Total Investment Income		12,834
Expenses:
Investment advisory fees		172,685
Distribution fees.		43,171
Dividend expense on securities sold short		84,264
Trustees’ fees		53,775
Shareholder communications expenses		42,412
Legal and audit fees		33,133
Shareholder services fees		31,440
Registration expenses		24,695
Service fees for securities sold short (see Note 2)		13,464
Custodian fees.		7,922
Interest expense		255
Miscellaneous expenses		29,906
Total Expenses		537,122
Net Investment Loss		(524,288	)
Net Realized and Unrealized Loss on Investments and Securities Sold Short:
Net realized loss on investments		(97,901	)
Net realized loss on securities sold short		(461,026	)
Net realized loss on investments and securities sold short		(558,927	)
Net change in unrealized appreciation/depreciation on securities sold short		(136,972	)
Net Realized and Unrealized Loss on Investments and Securities Sold Short		(695,899	)
Net Decrease in Net Assets Resulting from Operations	$	(1,220,187	)

See accompanying notes to financial statements.

6

GAMCO Mathers Fund

Statement of Changes in Net Assets

	Year Ended December 31, 2012			Year Ended December 31, 2011
Operations:
Net investment loss.		$    (524,288	)		$    (499,166	)
Net realized loss on investments, securities sold short, and foreign currency transactions		(558,927	)		(409,751	)
Net change in unrealized appreciation/depreciation on investments and securities sold short		(136,972	)		37,527
Net Decrease in Net Assets Resulting from Operations		(1,220,187	)		(871,390	)
Shares of Beneficial Interest Transactions:
Net increase/(decrease) in net assets from shares of beneficial interest transactions		4,031,061			(2,916,164	)
Net Increase/(Decrease) in Net Assets		2,810,874			(3,787,554	)
Net Assets:
Beginning of period		17,998,319			21,785,873
End of period (including undistributed net investment income of $0 and $0, respectively)		$20,809,193			$17,998,319

See accompanying notes to financial statements.

7

GAMCO Mathers Fund

Financial Highlights

Selected data for a share of beneficial interest out standing throughout each period:

	Year Ended December 31,
	2012			2011			2010			2009			2008
Operating Performance:
Net asset value, beginning of period		$    9.55			$    9.99			$  10.36			$  10.47			$  10.45
Net investment loss(a)		(0.28	)		(0.25	)		(0.25	)		(0.22	)		(0.06	)
Net realized and unrealized gain/(loss) on investments and securities sold short		(0.35	)		(0.19	)		(0.12	)		0.11			0.08
Total from investment operations		(0.63	)		(0.44	)		(0.37	)		(0.11	)		0.02
Distributions to Shareholders:
Net investment income		—			—			—			—			(0.00	)(b)
Total distributions		—			—			—			—			(0.00	)(b)
Redemption Fees(a)		—			—			—			0.00	(b)		0.00	(b)
Net Asset Value, End of Period		$    8.92			$    9.55			$    9.99			$  10.36			$  10.47
Total return†		(6.60	)%		(4.40	)%		(3.57	)%		(1.05	)%		0.20	%
Ratios to Average Net Assets and Supplemental Data:
Net assets, end of period (in 000’s)		$20,809			$17,998			$21,786			$23,532			$27,143
Ratio of net investment loss to average net assets		(3.04	)%		(2.54	)%		(2.40	)%		(2.11	)%		(0.55	)%
Ratio of operating expenses to average net assets		3.11	%		2.59	%		2.55	%		2.20	%		2.13	%
Ratio of operating expenses to average net assets excluding the effect of dividends on securities sold short		2.62	%		2.44	%		2.49	%		2.17	%		2.13	%
Portfolio turnover rate		3,328	%		1,638	%		475	%		556	%		9,150	%

† Total return represents aggregate total return of a hypothetical $1,000 investment at the beginning of the period and sold at the end of the period including reinvestment of distributions.

(a) Per share data is calculated using the average shares outstanding method.

(b) Amount represents less than $0.005 per share.

See accompanying notes to financial statements.

8

GAMCO Mathers Fund

Notes to Financial Statements

1. Organization. GAMCO Mathers Fund was organized on June 17, 1999 as a Delaware statutory trust. The Fund commenced investment operations on October 1, 1999 as the successor to the Mathers Fund, Inc. (the “Mathers Fund”) which was organized on March 31, 1965 as a Maryland corporation. The Mathers Fund commenced investment operations on August 19, 1965. The Fund is a diversified open-end management investment company registered under the Investment Company Act of 1940, as amended (the “1940 Act”). The Fund seeks to achieve capital appreciation over the long term in various market conditions without excessive risk of capital loss.

2. Significant Accounting Policies. The Fund’s financial statements are prepared in accordance with U.S. Generally Accepted Accounting Principles (“GAAP”), which may require the use of management estimates and assumptions. Actual results could differ from those estimates. The following is a summary of significant accounting policies followed by the Fund in the preparation of its financial statements.

Security Valuation. Portfolio securities listed or traded on a nationally recognized securities exchange or traded in the U.S. over-the-counter market for which market quotations are readily available are valued at the last quoted sale price or a market’s official closing price as of the close of business on the day the securities are being valued. If there were no sales that day, the security is valued at the average of the closing bid and asked prices or, if there were no asked prices quoted on that day, then the security is valued at the closing bid price on that day. If no bid or asked prices are quoted on such day, the security is valued at the most recently available price or, if the Board of Trustees (the “Board”) so determines, by such other method as the Board shall determine in good faith to reflect its fair market value. Portfolio securities traded on more than one national securities exchange or market are valued according to the broadest and most representative market, as determined by Gabelli Funds, LLC (the “Adviser”).

Portfolio securities primarily traded on a foreign market are generally valued at the preceding closing values of such securities on the relevant market, but may be fair valued pursuant to procedures established by the Board if market conditions change significantly after the close of the foreign market, but prior to the close of business on the day the securities are being valued. Debt instruments with remaining maturities of sixty days or less that are not credit impaired are valued at amortized cost, unless the Board determines such amount does not reflect the securities’ fair value, in which case these securities will be fair valued as determined by the Board. Debt instruments having a maturity greater than sixty days for which market quotations are readily available are valued at the average of the latest bid and asked prices. If there were no asked prices quoted on such day, the security is valued using the closing bid price. U.S. government obligations with maturities greater than sixty days are normally valued using a model that incorporates market observable data such as reported sales of similar securities, broker quotes, yields, bids, offers, and reference data. Certain securities are valued principally using dealer quotations.

Securities and assets for which market quotations are not readily available are fair valued as determined by the Board. Fair valuation methodologies and procedures may include, but are not limited to: analysis and review of available financial and non-financial information about the company; comparisons with the valuation and changes in valuation of similar securities, including a comparison of foreign securities with the equivalent U.S. dollar value American Depositary Receipt securities at the close of the U.S. exchange; and evaluation of any other information that could be indicative of the value of the security.

9

GAMCO Mathers Fund

Notes to Financial Statements (Continued)

The inputs and valuation techniques used to measure fair value of the Fund’s investments are summarized into three levels as described in the hierarchy below:

— Level 1 — quoted prices in active markets for identical securities;

— Level 2 — other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risk, etc.); and

— Level 3 — significant unobservable inputs (including the Fund’s determinations as to the fair value of investments).

A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input both individually and in the aggregate that is significant to the fair value measurement. The inputs or methodology used for valuing securities are not necessarily an indication of the risk associated with investing in those securities. The summary of the Fund’s investments in securities by inputs used to value the Fund’s investments as of December 31, 2012 is as follows:

	Valuation Inputs
	Level 1 Quoted Prices			Level 2 Other Significant Observable Inputs		Total Market Value at 12/31/12
INVESTMENTS IN SECURITIES:
ASSETS (Market Value):
Short-Term Obligations:
Repurchase Agreements		—			$     409,439		$     409,439
U.S. Government Obligations		—			20,599,931		20,599,931
TOTAL INVESTMENTS IN SECURITIES – ASSETS		—			$21,009,370		$21,009,370
LIABILITIES (Market Value):
Securities Sold Short(a)		$(6,969,902	)		—		$(6,969,902	)
TOTAL INVESTMENTS IN SECURITIES – LIABILITIES		$(6,969,902	)		—		$(6,969,902	)

(a) Please refer to the Schedule of Investments for the industry classifications of these portfolio holdings.

The Fund did not have transfers between Level 1 and Level 2 during the year ended December 31, 2012. The Fund’s policy is to recognize transfers among Levels as of the beginning of the reporting period.

There were no Level 3 investments held at December 31, 2012 or December 31, 2011.

Additional Information to Evaluate Qualitative Information.

    General. The Fund uses recognized industry pricing services – approved by the Board and unaffiliated with the Adviser – to value most of its securities, and uses broker quotes provided by market makers of securities not valued by these and other recognized pricing sources. Several different pricing feeds are received to value domestic equity securities, international equity securities, preferred equity securities, and fixed income securities. The data within these feeds is ultimately sourced from major stock exchanges and trading systems where these securities trade. The prices supplied by external sources are checked by obtaining quotations or actual transaction prices from market participants. If a price obtained from the pricing source is deemed unreliable, prices will be sought from another pricing service or from a broker/dealer that trades that security or similar securities.

    Fair Valuation. Fair valued securities may be common and preferred equities, warrants, options, rights, and fixed income obligations. Where appropriate, Level 3 securities are those for which market quotations are not available, such as securities not traded for several days, or for which current bids are not available, or

10

GAMCO Mathers Fund

Notes to Financial Statements (Continued)

which are restricted as to transfer. Among the factors to be considered to fair value a security are recent prices of comparable securities that are publicly traded, reliable prices of securities not publicly traded, the use of valuation models, current analyst reports, valuing the income or cash flow of the issuer, or cost if the preceding factors do not apply. The circumstances of Level 3 securities are frequently monitored to determine if fair valuation measures continue to apply.

The Adviser reports quarterly to the Board the results of the application of fair valuation policies and procedures. These include back testing the prices realized in subsequent trades of these fair valued securities to fair values previously recognized.

Derivative Financial Instruments. The Fund may engage in various portfolio investment strategies by investing in a number of derivative financial instruments for the purposes of hedging against changes in the value of its portfolio securities and in the value of securities it intends to purchase. Investing in certain derivative financial instruments, including participation in the options, futures, or swap markets, entails certain execution, liquidity, hedging, tax, and securities, interest, credit, or currency market risks. Losses may arise if the Adviser’s prediction of movements in the direction of the securities, foreign currency, and interest rate markets is inaccurate. Losses may also arise if the counterparty does not perform its duties under a contract, or that, in the event of default, the Fund may be delayed in or prevented from obtaining payments or other contractual remedies owed to it under derivative contracts. The creditworthiness of the counterparties is closely monitored in order to minimize these risks. Participation in derivative transactions involves investment risks, transaction costs, and potential losses to which the Fund would not be subject absent the use of these strategies. The consequences of these risks, transaction costs, and losses may have a negative impact on the Fund’s ability to pay distributions. There were no derivative securities held as of December 31, 2012.

The Fund’s derivative contracts held at December 31, 2012, if any, are not accounted for as hedging instruments under GAAP and are disclosed in the Schedule of Investments together with the related counterparty.

Repurchase Agreements. The Fund may enter into repurchase agreements with primary government securities dealers recognized by the Federal Reserve Board, with member banks of the Federal Reserve System, or with other brokers or dealers that meet credit guidelines established by the Adviser and reviewed by the Board. Under the terms of a typical repurchase agreement, the Fund takes possession of an underlying debt obligation subject to an obligation of the seller to repurchase, and the Fund to resell, the obligation at an agreed-upon price and time, thereby determining the yield during the Fund’s holding period. It is the policy of the Fund to receive and maintain securities as collateral whose market value is not less than their repurchase price. The Fund will make payment for such securities only upon physical delivery or upon evidence of book entry transfer of the collateral to the account of the custodian. To the extent that any repurchase transaction exceeds one business day, the value of the collateral is marked-to-market on a daily basis to maintain the adequacy of the collateral. If the seller defaults and the value of the collateral declines or if bankruptcy proceedings are commenced with respect to the seller of the security, realization of the collateral by the Fund may be delayed or limited. The repurchase agreement the Fund held at December 31, 2012 is reflected within the Schedule of Investments.

11

GAMCO Mathers Fund

Notes to Financial Statements (Continued)

Securities Sold Short. The Fund may enter into short sale transactions. Short selling involves selling securities that may or may not be owned and, at times, borrowing the same securities for delivery to the purchaser, with an obligation to replace such borrowed securities at a later date. The proceeds received from short sales are recorded as liabilities and the Fund records an unrealized gain or loss to the extent of the difference between the proceeds received and the value of an open short position on the day of determination. The Fund records a realized gain or loss when the short position is closed out. By entering into a short sale, the Fund bears the market risk of an unfavorable change in the price of the security sold short. Dividends on short sales are recorded as an expense by the Fund on the ex-dividend date and interest expense is recorded on the accrual basis. The broker retains collateral for the value of the open positions, which is adjusted periodically as the value of the position fluctuates. Securities sold short and details of collateral at December 31, 2012 are reflected within the Schedule of Investments. For the year ended December 31, 2012, the Fund incurred $13,464 in service fees related to its investment positions sold short held by the broker. The amount is included in the Statement of Operations - Expenses: Service fees for securities sold short.

Securities Transactions and Investment Income. Securities transactions are accounted for on the trade date with realized gain or loss on investments determined by using the identified cost method. Interest income (including amortization of premium and accretion of discount) is recorded on the accrual basis. Premiums and discounts on debt securities are amortized using the effective yield to maturity method. Dividend income is recorded on the ex-dividend date, except for certain dividends from foreign securities that are recorded as soon after the ex-dividend date as the Fund becomes aware of such dividends.

Expenses. Certain administrative expenses are common to, and allocated among, various affiliated funds. Such allocations are made on the basis of each fund’s average net assets or other criteria directly affecting the expenses as determined by the Adviser pursuant to procedures established by the Board.

Custodian Fee Credits and Interest Expense. When cash balances are maintained in the custody account, the Fund receives credits which are used to offset custodian fees. The gross expenses paid under the custody arrangement are included in custodian fees in the Statement of Operations with the corresponding expense offset, if any, shown as “Custodian fee credits.” When cash balances are overdrawn, the Fund is charged an overdraft fee equal to 2.00% above the federal funds rate on outstanding balances. This amount, if any, would be included in the Statement of Operations.

Distributions to Shareholders. Distributions to shareholders are recorded on the ex-dividend date. Distributions to shareholders are based on income and capital gains as determined in accordance with federal income tax regulations, which may differ from income and capital gains as determined under GAAP. These differences are primarily due to differing treatments of income and gains on various investment securities held by the Fund, timing differences, and differing characterizations of distributions made by the Fund. These book/ tax differences are either temporary or permanent in nature. To the extent these differences are permanent, adjustments are made to the appropriate capital accounts in the period when the differences arise. Permanent differences were primarily due to a write-off of the current year net operating loss, expiration of capital loss carryover, and reclassifications of short sale dividends. These reclassifications have no impact on the net asset value (“NAV”) per share of the Fund. For the year ended December 31, 2012, reclassifications were made to decrease accumulated net investment loss by $524,288 and decrease accumulated net realized loss on investments and securities sold short by $247,853, with an offsetting adjustment to paid-in capital.

12

GAMCO Mathers Fund

Notes to Financial Statements (Continued)

No distributions were made during the years ended December 31, 2012 and December 31, 2011.

Provision for Income Taxes. The Fund intends to continue to qualify as a regulated investment company under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”). It is the policy of the Fund to comply with the requirements of the Code applicable to regulated investment companies and to distribute substantially all of its net investment company taxable income and net capital gains. Therefore, no provision for federal income taxes is required.

As of December 31, 2012, the components of accumulated earnings/losses on a tax basis were as follows:

Accumulated capital loss carryforwards	$(1,771,414	)
Net unrealized depreciation on investments.	(987,832	)
Total	$(2,759,246	)

At December 31, 2012, the Fund had net capital loss carryforwards for federal income tax purposes which are available to reduce future required distributions of net capital gains to shareholders. Under the Regulated Investment Company Modernization Act of 2010, the Fund will be permitted to carry forward for an unlimited period capital losses incurred in years beginning after December 22, 2010. In addition, these losses must be utilized prior to the losses incurred in pre-enactment taxable years. As a result of the rule, pre-enactment capital loss carryforwards may have an increased likelihood of expiring unused. Additionally, post enactment capital losses that are carried forward will retain their character as either short-term or long-term capital losses rather than being considered all short-term as under previous law.

Capital Loss Carryforward Available through 2014	$1,096,894
Capital Loss Carryforward Available through 2018	151,917
Short-term Capital Loss Carryforward Post-Effective With No Expiration	522,603
Total Capital Loss Carryforwards.	$1,771,414

During the year ended December 31, 2012, capital loss carryforwards of $280,466 expired for the Fund.

At December 31, 2012, the differences between book basis and tax basis unrealized depreciation were primarily due to deferral of losses from wash sales for tax purposes.

The following summarizes the tax cost of investments, proceeds from short sales, and the related unrealized depreciation at December 31, 2012:

	Cost/ (Proceeds)			Gross Unrealized Appreciation		Gross Unrealized Depreciation			Net Unrealized Depreciation
Investments		$21,896,712			$        —		$   (887,342	)		$(887,342	)
Securities sold short		(6,869,412	)		55,587		(156,077	)		(100,490	)
					$55,587		$(1,043,419	)		$(987,832	)

The Fund is required to evaluate tax positions taken or expected to be taken in the course of preparing the Fund’s tax returns to determine whether the tax positions are “more-likely-than-not” of being sustained by the applicable tax authority. Income tax and related interest and penalties would be recognized by the Fund as tax expense in the Statement of Operations if the tax positions were deemed not to meet the more-likely-than-not threshold. For the year ended December 31, 2012, the Fund did not incur any income tax, interest, or penalties. As of December 31, 2012, the Adviser has reviewed all open tax years and concluded that there was no impact

13

GAMCO Mathers Fund

Notes to Financial Statements (Continued)

to the Fund’s net assets or results of operations. Tax years ended December 31, 2009 through December 31, 2012 remain subject to examination by the Internal Revenue Service and state taxing authorities. On an ongoing basis, the Adviser will monitor the Fund’s tax positions to determine if adjustments to this conclusion are necessary.

3. Investment Advisory Agreement and Other Transactions. The Fund has entered into an investment advisory agreement (the “Advisory Agreement”) with the Adviser which provides that the Fund will pay the Adviser a fee, computed daily and paid monthly, at the annual rate of 1.00% of the value of its average daily net assets. In accordance with the Advisory Agreement, the Adviser provides a continuous investment program for the Fund’s portfolio, oversees the administration of all aspects of the Fund’s business and affairs, and pays the compensation of all Officers and Trustees of the Fund who are affiliated persons of the Adviser.

The Fund pays each Trustee who is not considered an affiliated person an annual retainer of $3,000 plus $1,000 for each Board meeting attended, and they are reimbursed for any out of pocket expenses incurred in attending meetings. All Board committee members receive $500 per meeting attended and the Chairman of the Audit Committee and the Lead Trustee each receive an annual fee of $1,000. A Trustee may receive a single meeting fee, allocated among the participating funds, for participation in certain meetings held on behalf of multiple funds. Trustees who are directors or employees of the Adviser or an affiliated company receive no compensation or expense reimbursement from the Fund.

4. Distribution Plan. The Fund’s Board has adopted a distribution plan (the “Plan”) pursuant to Rule 12b-1 under the 1940 Act. Under the Plan, payments are authorized to G.distributors, LLC (the “Distributor”), an affiliate of the Fund at an annual rate of 0.25% of its average daily net assets, the annual limitation under the Plan. Such payments are accrued daily and paid monthly.

5. Portfolio Securities. Purchases and sales of securities during the year ended December 31, 2012, other than short-term securities and U.S. Government obligations, aggregated $1,136,448 and $1,035,268, respectively.

6. Line of Credit. The Fund participates in an unsecured line of credit of up to $75,000,000 under which it may borrow up to 10% of its net assets from the custodian for temporary borrowing purposes. Borrowings under this arrangement bear interest at the higher of the sum of the overnight LIBOR rate plus 100 basis points or the sum of the federal funds rate plus 100 basis points at the time of borrowing. This amount, if any, would be included in “interest expense” in the Statement of Operations. During the year ended December 31, 2012, there were no borrowings under the line of credit.

7. Shares of Beneficial Interest. Transactions in shares of beneficial interest were as follows:

	Year Ended December 31, 2012						Year Ended December 31, 2011
	Shares			Amount			Shares			Amount
Shares sold		783,209			$7,105,119			35,843			$    353,506
Shares redeemed		(335,237	)		(3,074,058	)		(331,102	)		(3,269,670	)
Net increase/(decrease)		447,972			$4,031,061			(295,259	)		$(2,916,164	)

14

GAMCO Mathers Fund

Notes to Financial Statements (Continued)

The Fund imposes a redemption fee of 2.00% on shares that are redeemed or exchanged on or before the seventh day after the date of a purchase. The redemption fee is deducted from the proceeds otherwise payable to the redeeming shareholders and is retained by the Fund as an increase in paid-in capital. The Fund did not retain any redemption fees during the years ended December 31, 2012 and December 31, 2011.

8. Indemnifications. The Fund enters into contracts that contain a variety of indemnifications. The Fund’s maximum exposure under these arrangements is unknown. However, the Fund has not had prior claims or losses pursuant to these contracts. Management has reviewed the Fund’s existing contracts and expects the risk of loss to be remote.

9. Other Matters. On April 24, 2008, the Adviser entered into a settlement with the SEC to resolve an inquiry regarding prior frequent trading in shares of the GAMCO Global Growth Fund (the “Global Growth Fund”) by one investor who was banned from the Global Growth Fund in August 2002. Under the terms of the settlement, the Adviser, without admitting or denying the SEC’s findings and allegations, paid $16 million (which included a $5 million civil monetary penalty). On the same day, the SEC filed a civil action in the U.S. District Court for the Southern District of New York against the Executive Vice President and Chief Operating Officer of the Adviser, alleging violations of certain federal securities laws arising from the same matter. The officer, who also is an officer of the Global Growth Fund and other funds in the Gabelli/GAMCO complex, including this Fund, denies the allegations and is continuing in his positions with the Adviser and the funds. The settlement by the Adviser did not have, and the resolution of the action against the officer is not expected to have, a material adverse impact on the Adviser or its ability to fulfill its obligations under the Advisory Agreement.

10. Subsequent Events. Management has evaluated the impact on the Fund of all subsequent events occurring through the date the financial statements were issued and has determined that there were no subsequent events requiring recognition or disclosure in the financial statements.

15

GAMCO Mathers Fund

Report of Independent Registered Public Accounting Firm

To the Shareholders and Board of Trustees of

GAMCO Mathers Fund:

We have audited the accompanying statement of assets and liabilities, including the schedule of investments, of GAMCO Mathers Fund (the “Fund”), as of December 31, 2012, and the related statement of operations for the year then ended, the statements of changes in net assets for each of the two years in the period then ended, and the financial highlights for each of the five years in the period then ended. These financial statements and financial highlights are the responsibility of the Fund’s management. Our responsibility is to express an opinion on these financial statements and financial highlights based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements and financial highlights are free of material misstatement. We were not engaged to perform an audit of the Fund’s internal control over financial reporting. Our audits included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Fund’s internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements and financial highlights, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. Our procedures included confirmation of securities owned as of December 31, 2012, by correspondence with the Fund’s custodian. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements and financial highlights referred to above present fairly, in all material respects, the financial position of the Fund at December 31, 2012, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period then ended, and its financial highlights for each of the five years in the period then ended, in conformity with U.S. generally accepted accounting principles.

New York, New York

February 28, 2013

16

GAMCO MATHERS FUND

Board Consideration and Re-Approval of Management Agreements (Unaudited)

At its meeting on August 14, 2012, the Board of Trustees (“Board”) of the Fund approved the continuation of the investment advisory agreement with the Adviser for the Fund on the basis of the recommendation by the trustees who are not “interested persons” (the “independent trustees”) of the Fund. The following paragraphs summarize the material information and factors considered by the independent trustees as well as their conclusions relative to such factors.

1. Nature, Extent, and Quality of Services.

The Board reviewed in detail the nature and extent of the services provided by the Adviser under the Agreement and the quality of those services over the past year. The Board noted that these services included managing the investment program of the Fund, including the purchase and sale of portfolio securities, as well as the provision of general corporate services. The Board considered that the Adviser also provided, at its expense, office facilities for use by the Fund and supervisory personnel responsible for supervising the performance of administrative, accounting, and related services for the Fund, including, net asset value determinations, yield calculations, and monitoring to assure compliance with stated investment policies and restrictions under the 1940 Act and related securities regulations. The Board noted that, in addition to managing the investment program for the Fund, the Adviser provided certain non-advisory and compliance services, including services under the Fund’s Rule 38a-1 compliance program.

The Board also considered that the Adviser paid for all compensation of officers and Board Members of the Fund that were affiliated with the Adviser and that the Adviser further provided services to shareholders of the Fund who had invested through various programs offered by third party financial intermediaries. The Board evaluated these factors based on its direct experience with the Adviser and in consultation with Fund Counsel. The Board noted that the Adviser had engaged, at its expense, BNY Mellon Investment Servicing (US) Inc. to assist it in performing certain of its administrative functions. The Board concluded that the nature and extent of the services provided was reasonable and appropriate in relation to the advisory fee, that the level of service provided by the Adviser, either directly or through BNY, had not diminished over the past year, and that the quality of service continued to be high.

The Board reviewed the personnel responsible for providing services to the Fund and concluded, based on their experience and interaction with the Adviser, that (i) the Adviser was able to retain quality personnel, (ii) the Adviser and its agents exhibited a high level of diligence and attention to detail in carrying out their advisory and administrative responsibilities under the Advisory Agreement, (iii) the Adviser was responsive to requests of the Board, (iv) the scope and depth of the Adviser’s resources was adequate, and (v) the Adviser had kept the Board apprised of developments relating to the Fund and the industry in general. The Board also focused on the Adviser’s reputation and long standing relationship with the Fund. The Board also believed that the Adviser had devoted substantial resources and made substantial commitments to address new regulatory compliance requirements applicable to the Fund.

2. The performance of the Fund, the Adviser.

The Board reviewed the investment performance of the Fund, on an absolute basis, as compared with its Lipper peer group of other SEC registered funds, and against the Fund’s broad based securities market benchmark as reflected in the Fund’s prospectus and annual report. The Board considered the Fund’s one, three, five and ten year average total return for the periods ended June 30, 2012, but placed greater emphasis on the Fund’s longer term performance. The peer group considered by the Board was developed by Lipper and was comprised

17

GAMCO MATHERS FUND

Board Consideration and Re-Approval of Management Agreements (Unaudited) (Continued)

of special diversified equity and dedicated short bias funds (the “Performance Peer Group”). The Board considered these comparisons helpful in their assessment as to whether the Adviser was obtaining for the Fund’s shareholders the total return performance that was available in the marketplace, given the Fund’s objectives, strategy, limitations, and restrictions. In reviewing the Fund’s performance, the Board noted that the Fund’s performance was above the median for the one year, three year, five year and ten year periods.

The Board also considered an analysis prepared by the portfolio manager comparing the Fund’s relatively lower net asset value volatility (based on annual total return standard deviations) with other actively managed “bear” funds and the S&P 500 Index. This analysis showed that the Fund’s returns were similar to this peer group but with lower annual volatility (due to the Fund’s relatively high cash position). The Board also considered the Adviser’s comment that the lower volatility reflected lower portfolio risk.

In connection with its assessment of the performance of the Adviser, the Board considered the Adviser’s financial condition and whether it had the resources necessary to continue to carry out its functions under the Advisory Agreement. The Board concluded that the Adviser had the financial resources necessary to continue to perform its obligations under the Advisory Agreement and to continue to provide the high quality services that it has provided to the Fund to date.

3. The cost of the advisory services and the profits to the Adviser and its affiliates from the relationship with the Fund.

In connection with the Board’s consideration of the cost of the advisory services and the profits to the Adviser and its affiliates from the relationship with the Fund, the Board considered a number of factors. First, the Board compared the level of the advisory fee for the Fund against comparative Lipper expense peer groups (“Expense Peer Group”). The Board also considered comparative non-management fee expenses and comparative total fund expenses of the Fund and the Expense Peer Group. The Board considered this information as useful in assessing whether the Adviser was providing services at a cost that was competitive with other similar funds. The Board noted that the Fund’s advisory fee was lower than average compared with those of the Expense Peer Group and the expense ratio was higher than average compared with those of the Expense Peer Group for the Fund.

The Board Members also reviewed the fees charged by the Adviser to provide similar advisory services to other registered investment companies or accounts with similar investment objectives, noting that in some cases the fees charged by the Adviser were the same, or lower, than the fees charged to the Fund.

The Board also considered an analysis prepared by the Adviser of the estimated profitability to the Adviser of its relationship with the Fund and reviewed with the Adviser its cost allocation methodology in connection with its profitability. In this regard, the Board reviewed Pro-forma Income Statements of the Adviser for the year ended December 31, 2011. The Board considered one analysis for the Adviser as a whole, and a second analysis for the Adviser with respect to the Fund. With respect to the Fund analysis, the Board received an analysis based on the Fund’s average net assets during the period as well as a pro-forma analysis of profitability at higher and lower asset levels. The Board concluded that the profitability of the Fund to the Adviser under either analysis was not excessive.

18

GAMCO MATHERS FUND

Board Consideration and Re-Approval of Management Agreements (Unaudited) (Continued)

4. The extent to which economies of scale will be realized as the Fund grows and whether fee levels reflect those economies of scale.

With respect to the Board’s consideration of economies of scale, the Board discussed whether economies of scale would be realized by the Fund at higher asset levels. The Board also reviewed data from the Expense Peer Group to assess whether the Expense Peer Group funds had advisory fee breakpoints and, if so, at what asset levels. The Board also assessed whether certain of the Adviser’s costs would increase if asset levels rise. The Board concluded that under foreseeable conditions, they were unable to assess at this time whether economies of scale would be realized by the Fund if it were to experience significant asset growth. In the event there was to be significant asset growth in the Fund, the Board determined to reassess whether the advisory fee appropriately took into account any economies of scale that had been realized as a result of that growth.

5. Other Factors.

In addition to the above factors, the Board also discussed other benefits received by the Adviser from its management of the Fund. The Board considered that the Adviser does use soft dollars in connection with its management of the Fund.

Based on a consideration of all these factors in their totality, the Board Members, including all of the Independent Board Members, determined that the Fund’s advisory fee was fair and reasonable with respect to the quality of services provided and in light of the other factors described above that the Board deemed relevant. Accordingly, the Board Members determined to approve the continuation of the Fund’s Advisory Agreement. The Board based its decision on evaluations of all these factors as a whole and did not consider any one factor as all important or controlling.

19

GAMCO Mathers Fund

Additional Fund Information (Unaudited)

The business and affairs of the Fund are managed under the direction of the Fund’s Board of Trustees. Information pertaining to the Trustees and officers of the Fund is set forth below. The Fund’s Statement of Additional Information includes additional information about the Fund’s Trustees and is available without charge, upon request, by calling 800-GABELLI (800-422-3554) or by writing to GAMCO Mathers Fund at One Corporate Center, Rye, NY 10580-1422.

Name, Position(s) Address1 and Age	Term of Office and Length of Time Served2	Number of Funds in Fund Complex Overseen by Trustee	Principal Occupation(s) During Past Five Years	Other Directorships Held by Trustee5
INTERESTED TRUSTEES3 :
Mario J. Gabelli, CFA Trustee and Chairman Age: 70	Since 1999	27	Chairman, Chief Executive Officer, and Chief Investment Officer–Value Portfolios of GAMCO Investors, Inc. and Chief Investment Officer–Value Portfolios of Gabelli Funds, LLC, and GAMCO Asset Management Inc.; Director/Trustee or Chief Investment Officer of other registered investment companies in the Gabelli/GAMCO Funds Complex; Chief Executive Officer of GGCP, Inc.	Director of Morgan Group Holdings, Inc. (holding company); Chairman of the Board and Chief Executive Officer of LICT Corp. (multimedia and communication services); Director of CIBL, Inc. (broadcasting and wireless communications); Director of RLJ Acquisition Inc. (blank check company) (2011-2012)
Henry G. Van der Eb, CFA4 Trustee, President and Chief Executive Officer Age: 67	Since 1976	2	Senior Vice President of GAMCO Investors, Inc. since August 2004; President and CEO of GAMCO Mathers Fund since 1999; Senior Vice President and Portfolio Manager of Gabelli Funds, LLC and GAMCO Asset Management Inc. since 1999; Chairman of Comstock Funds, Inc. since 2000	—
INDEPENDENT TRUSTEES6 :
M. Bruce Adelberg Trustee Age: 76	Since 2009	2	Consultant, MBA Research Group	—
E. Val Cerutti Trustee Age: 73	Since 2001	7	Chief Executive Officer of Cerutti Consultants, Inc.	Director of the LGL Group, Inc. (diversified manufacturing) (1990-2009)
Anthony S. Colavita Trustee Age: 51	Since 2009	2	Attorney, Anthony S. Colavita, P.C.	—
Vincent D. Enright Trustee Age: 69	Since 1999	17	Former Senior Vice President and Chief Financial Officer of KeySpan Corporation (public utility) (1994-1998)	Director of Echo Therapeutics, Inc. (therapeutics and diagnostics); and Director of the LGL Group, Inc. (diversified manufacturing)
Anthony R. Pustorino Trustee Age: 87	Since 1999	13	Certified Public Accountant; Professor Emeritus, Pace University	Director of The LGL Group, Inc. (diversified manufacturing) (2002-2010)
Werner J. Roeder, MD Trustee Age: 72	Since 1999	22	Medical Director of Lawrence Hospital and practicing private physician	—
Anthonie C. van Ekris Trustee Age: 78	Since 1999	20	Chairman and Chief Executive Officer of BALMAC International, Inc. (commodities and futures trading)	—

20

GAMCO Mathers Fund

Additional Fund Information (Continued) (Unaudited)

Name, Position(s) Address1 and Age	Term of Office and Length of Time Served2	Principal Occupation(s) During Past Five Years
OFFICERS:
Bruce N. Alpert Executive Vice President, Secretary, and Acting Chief Compliance Officer Age: 61	Since 1999	Executive Vice President and Chief Operating Officer of Gabelli Funds, LLC since 1988; Officer of all of the registered investment companies in the Gabelli/GAMCO Funds
	Since November 2011	Complex; Director of Teton Advisors, Inc. 1998-2012; Chairman of Teton Advisors, Inc. 2008-2010; President of Teton Advisors, Inc. 1998-2008; Senior Vice President of GAMCO Investors, Inc. since 2008
Edith L. Cook4 Vice President Age: 71	Since 1984	Vice President of GAMCO Mathers Fund since 1999
Heidi M. Koontz4 Vice President Age: 44	Since 1995	Vice President of GAMCO Mathers Fund since 1999
Agnes Mullady Treasurer Age: 54	Since 2006	President and Chief Operating Officer of the Open-End Fund Division of Gabelli Funds, LLC since September 2010; Senior Vice President of GAMCO Investors, Inc. since 2009; Vice President of Gabelli Funds, LLC since 2007; Officer of all of the registered investment companies in the Gabelli/GAMCO Funds Complex
Anne E. Morrissy, CFA4 Executive Vice President Age: 50	Since 1987	Executive Vice President of GAMCO Mathers Fund and Vice President of GAMCO Investors, Inc. since 1999

¹  Address: One Corporate Center, Rye, NY 10580-1422, unless otherwise noted.

²  Each Trustee will hold office for an indefinite term until the earliest of (i) the next meeting of shareholders, if any, called for the purpose of considering the election or re-election of such Trustee and until the election and qualification of his or her successor, if any, elected at such meeting, or (ii) the date a Trustee resigns or retires, or a Trustee is removed by the Board of Trustees or shareholders, in accordance with the Fund’s By-Laws and Declaration of Trust. Each officer will hold office for an indefinite term until the date he or she resigns or retires or until his or her successor is elected and qualified.

³  “Interested person” of the Fund as defined in the 1940 Act. Messrs. Gabelli and Van der Eb are each considered an “interested person” because of their affiliation with Gabelli Funds, LLC which acts as the Fund’s investment adviser.

⁴  Address: 2801 Lakeside Drive, Suite 201, Bannockburn, IL 60015.

⁵  This column includes only directorships of companies required to report to the SEC under the Securities Exchange Act of 1934, as amended, i.e., public companies, or other investment companies registered under the 1940 Act.

⁶  Trustees who are not interested persons are considered “Independent” Trustees.

21

Gabelli/GAMCO Funds and Your Personal Privacy

Who are we?

The Gabelli/GAMCO Funds are investment companies registered with the Securities and Exchange Commission under the Investment Company Act of 1940. We are managed by Gabelli Funds, LLC, which is affiliated with GAMCO Investors, Inc. GAMCO Investors, Inc. is a publicly held company that has subsidiaries that provide investment advisory or brokerage services for a variety of clients.

What kind of non-public information do we collect about you if you become a fund shareholder?

If you apply to open an account directly with us, you will be giving us some non-public information about yourself. The non-public information we collect about you is:

—   Information you give us on your application form. This could include your name, address, telephone number, social security number, bank account number, and other information.

—   Information about your transactions with us, any transactions with our affiliates, and transactions with the entities we hire to provide services to you. This would include information about the shares that you buy or redeem. If we hire someone else to provide services — like a transfer agent — we will also have information about the transactions that you conduct through them.

What information do we disclose and to whom do we disclose it?

We do not disclose any non-public personal information about our customers or former customers to anyone other than our affiliates, our service providers who need to know such information, and as otherwise permitted by law. If you want to find out what the law permits, you can read the privacy rules adopted by the Securities and Exchange Commission. They are in volume 17 of the Code of Federal Regulations, Part 248. The Commission often posts information about its regulations on its website, www.sec.gov.

What do we do to protect your personal information?

We restrict access to non-public personal information about you to the people who need to know that information in order to provide services to you or the fund and to ensure that we are complying with the laws governing the securities business. We maintain physical, electronic, and procedural safeguards to keep your personal information confidential.

22

GABELLI/GAMCO FAMILY OF FUNDS

VALUE                                                                

Gabelli Asset Fund

Seeks to invest primarily in a diversified portfolio of common stocks selling at significant discounts to their private market value. The Fund’s primary objective is growth of capital.

(Multiclass) Team Managed

Gabelli Dividend Growth Fund

Seeks to invest at least 80% of its net assets in dividend paying stocks. (Multiclass)

Portfolio Manager: Barbara G. Marcin, CFA

TETON Westwood Equity Fund

Seeks to invest primarily in the common stock of well seasoned companies that have recently reported positive earnings surprises and are trading below Westwood’s proprietary growth rate estimates. The Fund’s primary objective is capital appreciation.

(Multiclass) Team Managed

FOCUSED VALUE                                                   

Gabelli Focus Five Fund 

Seeks to invest up to 50% of its net assets in the equity securities of five companies with the remaining net assets invested in ten to twenty other companies or in short-term high grade investments or cash and cash equivalents.

(Multiclass) Team Managed

Gabelli Value Fund

Seeks to invest in securities of companies believed to be undervalued. The Fund’s primary objective is long-term capital appreciation. (Multiclass)         Team Managed

SMALL CAP                                                         

Gabelli Small Cap Growth Fund

Seeks to invest primarily in common stock of smaller companies (market capitalizations at the time of investment of $2 billion or less) believed to have rapid revenue and earnings growth potential. The Fund’s primary objective is capital appreciation. (Multiclass)

Portfolio Manager: Mario J. Gabelli, CFA

TETON Westwood SmallCap Equity Fund

Seeks to invest primarily in smaller capitalization equity securities – market caps of $2.5 billion or less. The Fund’s primary objective is long-term capital appreciation.

(Multiclass) Portfolio Manager: Nicholas F. Galluccio

GROWTH                                                             

GAMCO Growth Fund

Seeks to invest primarily in large cap stocks believed to have favorable, yet undervalued, prospects for earnings growth. The Fund’s primary objective is capital appreciation.

(Multiclass) Portfolio Manager: Howard F. Ward, CFA

GAMCO International Growth Fund

Seeks to invest in the equity securities of foreign issuers with long-term capital appreciation potential. The Fund offers investors global diversification.

(Multiclass) Portfolio Manager: Caesar Bryan

AGGRESSIVE GROWTH                                            

GAMCO Global Growth Fund

Seeks capital appreciation through a disciplined investment program focusing on the globalization and interactivity of the world’s marketplace. The Fund invests in companies at the forefront of accelerated growth. The Fund’s primary objective is capital appreciation. (Multiclass)

Team Managed

MICRO-CAP                                                         

TETON Westwood Mighty Mites^SM Fund

Seeks to invest in micro-cap companies that have market capitalizations of $500 million or less. The Fund’s primary objective is long-term capital appreciation. (Multiclass)

Team Managed

EQUITY INCOME                                                    

Gabelli Equity Income Fund

Seeks to invest primarily in equity securities with above average market yields. The Fund pays monthly distributions and seeks a high level of total return with an emphasis on income. (Multiclass)

Portfolio Manager: Mario J. Gabelli, CFA

TETON Westwood Balanced Fund

Seeks to invest in a balanced and diversified portfolio of stocks and bonds. The Fund’s primary objective is both capital appreciation and current income. (Multiclass)

Team Managed

TETON Westwood Income Fund

Seeks to provide a high level of current income as well as long-term capital appreciation by investing in income producing equity and fixed income securities. (Multiclass)

Portfolio Manager: Barbara G. Marcin, CFA

SPECIALTY EQUITY                                                

GAMCO Vertumnus Fund

Seeks to invest principally in common stock and convertible securities of domestic and foreign companies. The Fund’s primary objective is total return through a combination of current income and capital appreciation. (Multiclass)

Portfolio Manager: Mario J. Gabelli, CFA

GAMCO Global Opportunity Fund

Seeks to invest in common stock of companies which have rapid growth in revenues and earnings and potential for above average capital appreciation or are undervalued. The Fund’s primary objective is capital appreciation. (Multiclass)

Team Managed

Gabelli SRI Green Fund

Seeks to invest in common and preferred stocks meeting guidelines for social responsibility (avoiding defense contractors and manufacturers of alcohol, abortifacients, gaming, and tobacco products) and sustain ability (companies engaged in climate change, energy security and independence, natural resource shortages, organic living, and urbanization). The Fund’s primary objective is capital appreciation. (Multiclass)

Team Managed

SECTOR                                                              

GAMCO Global Telecommunications Fund

Seeks to invest in telecommunications companies throughout the world – targeting undervalued companies with strong earnings and cash flow dynamics. The Fund’s primary objective is capital appreciation. (Multiclass) Team Managed

Gabelli Gold Fund

Seeks to invest in a global portfolio of equity securities of gold mining and related companies. The Fund’s objective is long-term capital appreciation. Investment in gold stocks is considered speculative and is affected by a variety of worldwide economic, financial, and political factors.

(Multiclass) Portfolio Manager: Caesar Bryan

Gabelli Utilities Fund

Seeks to provide a high level of total return through a combination of capital appreciation and current income.

(Multiclass) Portfolio Manager: Mario J. Gabelli, CFA

MERGER AND ARBITRAGE                                       

Gabelli ABC Fund

Seeks to invest in securities with attractive opportunities for appreciation or investment income. The Fund’s primary objective is total return in various market conditions without excessive risk of capital loss. (No-load) (Multiclass)

Portfolio Manager: Mario J. Gabelli, CFA

Gabelli Enterprise Mergers and Acquisitions Fund

Seeks to invest in securities believed to be likely acquisition targets within 12–18 months or in arbitrage transactions of publicly announced mergers or other corporate reorganizations. The Fund’s primary objective is capital appreciation. (Multiclass)

Portfolio Manager: Mario J. Gabelli, CFA

CONTRARIAN                                                        

GAMCO Mathers Fund

Seeks long-term capital appreciation in various market conditions without excessive risk of capital loss. (No-load)

Portfolio Manager: Henry Van der Eb, CFA

Comstock Capital Value Fund

Seeks capital appreciation and current income. The Fund may use either long or short positions to achieve its objective. (Multiclass)

Portfolio Managers: Charles L. Minter

Martin Weiner, CFA

FIXED INCOME                                                      

TETON Westwood Intermediate Bond Fund

Seeks to invest in a diversified portfolio of bonds with various maturities. The Fund’s primary objective is total return. (Multiclass)

Portfolio Manager: Mark R. Freeman, CFA

CASH MANAGEMENT-MONEY MARKET                        

Gabelli U.S. Treasury Money Market Fund

Seeks to invest exclusively in short-term U.S. Treasury securities. The Fund’s primary objective is to provide high current income consistent with the preservation of principal and liquidity. (No-load)

Co-Portfolio Managers: Judith A. Raneri

Ronald S. Eaker

An investment in the above Money Market Fund is neither insured nor guaranteed by the Federal Deposit Insurance Corporation or any government agency. Although the Fund seeks to preserve the value of your investment at $1.00per share, it is possible to lose money by investing in the Fund.

The Funds may invest in foreign securities which involve risks not ordinarily associated with investments in domestic issues, including currency fluctuation, economic, and political risks.

To receive a prospectus, call 800-GABELLI (800-422-3554). Investors should carefully consider the investment objectives, risks, charges, and expenses of a fund before investing. The prospectus contains more information about these and other matters and should be read carefully before investing.

Distributed by G.distributors, LLC, One Corporate Center, Rye, NY 10580.

GAMCO MATHERS FUND

One Corporate Center

Rye, New York 10580-1422

t  800-GABELLI (800-422-3554)

f  914-921-5118

e info@gabelli.com

   GABELLI.COM

Net Asset Value per share available daily by calling 800-GABELLI after 7:00 P.M.
BOARD OF TRUSTEES	OFFICERS
Mario J. Gabelli, CFA	Bruce N. Alpert
Chairman and	Executive Vice President,
Chief Executive Officer,	Secretary, and Acting
GAMCO Investors, Inc.	Chief Compliance Officer
M. Bruce Adelberg	Agnes Mullady
Consultant,	Treasurer
MBA Research Group	Anne E. Morrissy, CFA Executive Vice President
E. Val Cerutti
Chief Executive Officer,	Heidi M. Koontz Vice President Edith L. Cook Vice President
Cerutti Consultants, Inc.
Anthony S. Colavita
Attorney,
Anthony S. Colavita, P.C.
Vincent D. Enright	DISTRIBUTOR
Former Senior Vice President	G.distributors, LLC CUSTODIAN, TRANSFER AGENT, AND DIVIDEND DISBURSING AGENT State Street Bank and Trust Company
and Chief Financial Officer,
KeySpan Corp.
Anthony R. Pustorino
Certified Public Accountant,
Professor Emeritus,
Pace University
Werner J. Roeder, MD	LEGAL COUNSEL
Medical Director,	Paul Hastings LLP
Lawrence Hospital
Henry G. Van der Eb, CFA
President and Chief Executive
Officer,
GAMCO Mathers Fund
Anthonie C. van Ekris
Chairman,
BALMAC International, Inc.

This report is submitted for the general information of the shareholders of the GAMCO Mathers Fund. It is not authorized for distribution to prospective investors unless preceded or accompanied by an effective prospectus.

GAB1726Q412AR

Item 2. Code of Ethics.

(a) The registrant, as of the end of the period covered by this report, has adopted a code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party.

(c) There have been no amendments, during the period covered by this report, to a provision of the code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, and that relates to any element of the code of ethics description.

(d) The registrant has not granted any waivers, including an implicit waiver, from a provision of the code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, that relates to one or more of the items set forth in paragraph (b) of this item’s instructions.

Item 3. Audit Committee Financial Expert.

As of the end of the period covered by the report, the registrant’s Board of Trustees has determined that Anthony R. Pustorino is qualified to serve as an audit committee financial expert serving on its audit committee and that he is “independent,” as defined by Item 3 of Form N-CSR.

Item 4. Principal Accountant Fees and Services.

Audit Fees

(a) The aggregate fees billed for each of the last two fiscal years for professional services rendered by the principal accountant for the audit of the registrant’s annual financial statements or services that are normally provided by the accountant in connection with statutory and regulatory filings or engagements for those fiscal years are $21,600 for 2011 and $22,300 for 2012.

Audit-Related Fees

(b) The aggregate fees billed in each of the last two fiscal years for assurance and related services by the principal accountant that are reasonably related to the performance of the audit of the registrant’s financial statements and are not reported under paragraph (a) of this Item are $0 for 2011 and $0 for 2012.

Tax Fees

(c) The aggregate fees billed in each of the last two fiscal years for professional services rendered by the principal accountant for tax compliance, tax advice, and tax planning are $3,200 for 2011 and $3,300 for 2012. Tax fees represent tax compliance services provided in connection with the review of the Registrant’s tax returns.

All Other Fees

(d) The aggregate fees billed in each of the last two fiscal years for products and services provided by the principal accountant, other than the services reported in paragraphs (a) through (c) of this Item are $0 for 2011 and $0 for 2012.

(e)(1) Disclose the audit committee’s pre-approval policies and procedures described in paragraph (c)(7) of Rule 2-01 of Regulation S-X.

Pre-Approval Policies and Procedures. The Audit Committee (“Committee”) of the registrant is responsible for pre-approving (i) all audit and permissible non-audit services to be provided by the independent registered public accounting firm to the registrant and (ii) all permissible non-audit services to be provided by the independent registered public accounting firm to the Adviser, Gabelli Funds, LLC, and any affiliate of Gabelli Funds, LLC (“Gabelli”) that provides services to the registrant (a “Covered Services Provider”) if the independent registered public accounting firm’s engagement related directly to the operations and financial reporting of the registrant. The Committee may delegate its responsibility to pre-approve any such audit and permissible non-audit services to the Chairperson of the Committee, and the Chairperson must report to the Committee, at its next regularly scheduled meeting after the Chairperson’s pre-approval of such services, his or her decision(s). The Committee may also establish detailed pre-approval policies and procedures for pre-approval of such services in accordance with applicable laws, including the delegation of some or all of the Committee’s pre-approval responsibilities to the other persons (other than Gabelli or the registrant’s officers). Pre-approval by the Committee of any permissible non-audit services is not required so long as: (i) the permissible non-audit services were not recognized by the registrant at the time of the engagement to be non-audit services; and (ii) such services are promptly brought to the attention of the Committee and approved by the Committee or Chairperson prior to the completion of the audit.

(e)(2) The percentage of services described in each of paragraphs (b) through (d) of this Item that were approved by the audit committee pursuant to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X are as follows:

(b) N/A

(c) 100%

(d) N/A

(f) The percentage of hours expended on the principal accountant’s engagement to audit the registrant’s financial statements for the most recent fiscal year that were attributed to work performed by persons other than the principal accountant’s full-time, permanent employees was 0%.

(g) The aggregate non-audit fees billed by the registrant’s accountant for services rendered to the registrant, and rendered to the registrant’s investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant for each of the last two fiscal years of the registrant was $49,500 for 2011 and $29,100 for 2012.

(h) The registrant’s audit committee of the board of directors has considered whether the provision of non-audit services that were rendered to the registrant’s investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence.

Item 5. Audit Committee of Listed registrants.

Not applicable.

Item 6. Investments.

(a) Schedule of Investments in securities of unaffiliated issuers as of the close of the reporting period is included as part of the report to shareholders filed under Item 1 of this form.

(b) Not applicable.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies.

Not applicable.

Item 8. Portfolio Managers of Closed-End Management Investment Companies.

Not applicable.

Item 9. Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers.

Not applicable.

Item 10. Submission of Matters to a Vote of Security Holders.

There have been no material changes to the procedures by which the shareholders may recommend nominees to the registrant’s Board of Trustees, where those changes were implemented after the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-K (17 CFR 229.407) (as required by Item 22(b)(15) of Schedule 14A (17 CFR 240.14a-101)), or this Item.

Item 11. Controls and Procedures.

(a) The registrant’s principal executive and principal financial officers, or persons performing similar functions, have concluded that the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the “1940 Act”) (17 CFR 270.30a-3(c))) are effective, as of a date within 90 days of the filing date of the report that includes the disclosure required by this paragraph, based on their evaluation of these controls and procedures required by Rule 30a-3(b) under the 1940 Act (17 CFR 270.30a-3(b)) and Rules 13a-15(b) or 15d-15(b) under the Securities Exchange Act of 1934, as amended (17 CFR 240.13a-15(b) or 240.15d-15(b)).

(b) There were no changes in the registrant’s internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act (17 CFR 270.30a-3(d)) that occurred during the registrant’s second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Exhibits.

(a)(1) Code of ethics, or any amendment thereto, that is the subject of disclosure required by Item 2 is attached hereto.

(a)(2) Certifications pursuant to Rule 30a-2(a) under the 1940 Act and Section 302 of the Sarbanes-Oxley Act of 2002 are attached hereto.

(a)(3) Not applicable.

(b) Certifications pursuant to Rule 30a-2(b) under the 1940 Act and Section 906 of the Sarbanes-Oxley Act of 2002 are attached hereto.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant) The GAMCO Mathers Fund

By (Signature and Title)*	/s/ Henry G. Van der Eb
	Henry G. Van der Eb, Chief Executive Officer

Date 3/8/2013

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*	/s/ Henry G. Van der Eb
	Henry G. Van der Eb, Chief Executive Officer

Date 3/8/2013

By (Signature and Title)*	/s/ Agnes Mullady
	Agnes Mullady, Principal Financial Officer and Treasurer

Date 3/8/2013

^* Print the name and title of each signing officer under his or her signature.