THE GABELLI DIVIDEND GROWTH FUND

Supplement dated September 14, 2017

to the

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 (the “SAI”), each dated April 28, 2017, of The Gabelli Dividend Growth Fund (the “Fund”). 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.

Portfolio Managers

Effective September 18, 2017, Sarah Donnelly will replace Barbara G. Marcin as a portfolio manager of the Fund.

Mr. Robert Leininger, CFA, Portfolio Manager of the Adviser, and Mr. Justin Bergner, CFA, Portfolio Manager of the Adviser and Vice President at Gabelli & Company, are continuing in their roles as portfolio managers of the Fund, roles they have held since March 2017.

Sarah Donnelly serves as a portfolio manager for Gabelli Funds, LLC. She is also a Senior Vice President of Gabelli & Company and has been a research analyst covering food, household, and personal care products. Ms. Donnelly joined GAMCO Investors, Inc. in 1999 as a junior research analyst working with the consumer staples and media analysts. She received a B.S. in Business Administration with a concentration in Finance and minor in History from Fordham University and currently serves on the advisory board of the Gabelli Center for Global Security Analysis at Fordham University.

Below is additional information about the new portfolio manager’s other accounts managed, compensation and ownership of securities in the Fund.

New Portfolio Manager – Other Accounts Managed

The information below provides summary information regarding other accounts for which the new portfolio manager was primarily responsible for the day to day management as of July 31, 2017.

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Potential Conflicts of Interest (All Portfolio Managers)

Actual or apparent conflicts of interest may arise when the portfolio managers also have day to day management responsibilities with respect to one or more other accounts. These potential conflicts include:

Allocation of Limited Time and Attention. Because the portfolio managers manage more than one account, they may not be able to formulate as complete a strategy or identify equally attractive investment opportunities for each of those accounts as if they were to devote substantially more attention to the management of only the Fund.

Allocation of Limited Investment Opportunities. If the portfolio managers identify an investment opportunity that may be suitable for multiple accounts, the Fund may not be able to take full advantage of that opportunity because the opportunity may need to be allocated among these accounts or other accounts managed primarily by other portfolio managers of the Adviser and its affiliates.

Pursuit of Differing Strategies. At times, the portfolio managers may determine that an investment opportunity may be appropriate for only some of the accounts for which they exercise investment responsibility, or may decide that certain of these accounts should take differing positions with respect to a particular security. In these cases, the portfolio managers may execute differing or opposite transactions for one or more accounts which may affect the market price of the security or the execution of the transactions, or both, to the detriment of one or more other accounts.

Selection of Broker/Dealers. A portfolio manager may be able to select or influence the selection of the brokers and dealers that are used to execute securities transactions for the funds or accounts that they supervise. In addition to providing execution of trades, some brokers and dealers provide the Adviser with brokerage and research services which may result in the payment of higher brokerage fees than might otherwise be available. These services may be more beneficial to certain funds or accounts of the Adviser and its affiliates than to others. Although the payment of brokerage commissions is subject to the requirement that the Adviser determines in good faith that the commissions are reasonable in relation to the value of the brokerage and research services provided to the Fund, a portfolio manager’s decision as to the selection of brokers and dealers could yield disproportionate costs and benefits among the funds or other accounts that the Adviser and its affiliates manage. In addition, with respect to certain types of accounts (such as pooled investment vehicles and other accounts managed for organizations and individuals), the Adviser may be limited by the client concerning the selection of brokers or may be instructed to direct trades to particular brokers. In these cases, the Adviser or its affiliates may place separate, non-simultaneous transactions in the same security for the Fund and another account that may temporarily affect the market price of the security or the execution of the transaction, or both, to the detriment of the Fund or the other accounts.

Variation in Compensation. A conflict of interest may arise where the financial or other benefits available to a portfolio manager differ among the accounts that they manage. If the structure of the Adviser’s management fee or a portfolio manager’s compensation differs among accounts (such as where certain accounts pay higher management fees or performance based management fees), a portfolio manager may be motivated to favor certain accounts over others. A portfolio manager also may be motivated to favor accounts in which they have an investment interest, or in which the Adviser or its affiliates have investment interests. Similarly, the desire to maintain assets under management or to enhance a portfolio manager’s performance record or to derive other rewards, financial or otherwise, could influence a portfolio manager in affording preferential treatment to those accounts that could most significantly benefit the portfolio manager.

The Adviser and the Fund have adopted compliance policies and procedures that are reasonably designed to address the various conflicts of interest that may arise for the Adviser and its staff members. However, there is no guarantee that such policies and procedures will be able to detect and address every situation in which an actual or potential conflict may arise.

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All Portfolio Managers – Compensation Structure as of July 31, 2017

The compensation of portfolio managers in the Gabelli organization is structured to enable the Adviser to attract and retain highly qualified professionals in a competitive environment. The portfolio managers receive a compensation package that includes a minimum draw or base salary, equity-based incentive compensation via awards of stock options and restricted stock, and incentive-based variable compensation based on a percentage of net revenues received by the Adviser for managing the Fund to the extent that the amount exceeds a minimum level of compensation. Net revenues are determined by deducting from gross investment management fees certain of the Firm’s expenses (other than the respective portfolio manager’s compensation) allocable to the Fund (the incentive based variable compensation for managing other accounts is also based on a percentage of net revenues to the investment adviser for managing the account). Certain portfolio managers receive similar incentive based variable compensation for managing other accounts for GAMCO Asset Management Inc.

The compensation for managing accounts that have a performance based fee will have two components. One component is based on a percentage of net revenues received by the adviser for managing the account. The second component is based on absolute performance of the account, with respect to which a percentage of the net performance fee is paid to the portfolio manager.

These methods of compensation are based on the premise that superior long term performance in managing a portfolio should be rewarded with higher compensation as a result of growth of assets through appreciation and net investment activity. The level of equity based incentive and incentive-based variable compensation is based on an evaluation by the Adviser’s parent, GBL, of quantitative and qualitative performance evaluation criteria.

New Portfolio Manager – Ownership of Shares in the Fund

Set forth in the table below is the dollar range of equity securities in the Fund beneficially owned by the Fund’s new portfolio manager as of July 31, 2017:

Shareholders Should Retain This Supplement For Future Reference

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