Eaton Vance Tax Managed Diversified Equity Income Fund : Full Prospectus

Prospectus Supplement

(To Prospectus dated February 19, 2021)

Eaton Vance Tax-Managed Diversified Equity Income Fund

Up to 11,231,109 Common Shares

Eaton Vance Tax-Managed Diversified Equity Income Fund (the "Fund," "we," or "our") is a diversified, closed-end management investment company which commenced operations on November 27, 2006. Our investment objective is to provide current income and gains, with a secondary objective of capital appreciation.

The Fund has entered into a distribution agreement dated May 9, 2019 (the "Distribution Agreement") with Eaton Vance Distributors, Inc. (the "Distributor") relating to the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus dated February 19, 2021. The Distributor has entered into a dealer agreement, dated May 9, 2019 (the "Dealer Agreement") with UBS Securities LLC (the "Dealer") with respect to the Fund relating to the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus. In accordance with the terms of the Dealer Agreement, we may offer and sell our Common Shares, $0.01 par value per share, from time to time through the Dealer as sub-placement agent for the offer and sale of the Common Shares. Under the Investment Company Act of 1940, as amended (the "1940 Act"), the Fund may not sell any Common Shares at a price below the current net asset value of such Common Shares, exclusive of any distributing commission or discount.

Our Common Shares are listed on the New York Stock Exchange ("NYSE") under the symbol "ETY." As of February 17, 2021, the last reported sales price for our Common Shares on the NYSE was $12.78 per share.

Sales of our Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus may be made in negotiated transactions or transactions that are deemed to be "at the market" as defined in Rule 415 under the Securities Act of 1933, as amended (the "1933 Act"), including sales made directly on the NYSE or sales made to or through a market maker other than on an exchange.

The Fund will compensate the Distributor with respect to sales of the Common Shares at a commission rate of 1.00% of the gross proceeds of the sale of Common Shares. The Distributor will compensate the Dealer out of this commission at a certain percentage rate of the gross proceeds of the sale of Common Shares sold under the Dealer Agreement, with the exact amount of such compensation to be mutually agreed upon by the Distributor and the Dealer from time to time. In connection with the sale of the Common Shares on the Fund's behalf, the Distributor may be deemed to be an "underwriter" within the meaning of the 1933 Act and the compensation of the Dealer may be deemed to be underwriting commissions or discounts.

The Common Shares have traded both at a premium and a discount to net asset value ("NAV"). The Fund cannot predict whether Common Shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company's common stock (calculated within 48 hours of pricing). The Fund's issuance of Common Shares may have an adverse effect on prices in the secondary market for the Fund's Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for the Fund's Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV, which may increase investors' risk of loss.

Investing in our securities involves certain risks. You could lose some or all of your investment. See "Investment Objectives, Policies and Risks" beginning on page 25 of the accompanying Prospectus. You should consider carefully these risks together with all of the other information contained in this Prospectus Supplement and the accompanying Prospectus before making a decision to purchase our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus Supplement or the accompanying Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Prospectus Supplement dated February 19, 2021

This Prospectus Supplement, together with the accompanying Prospectus, sets forth concisely information about the Fund that you should know before investing. You should read this Prospectus Supplement and the accompanying Prospectus, which contain important information, before deciding whether to invest in our securities. You should retain the accompanying Prospectus and this Prospectus Supplement for future reference. A Statement of Additional Information ("SAI"), dated February 19, 2021 as supplemented from time to time, containing additional information about the Fund, has been filed with the Securities and Exchange Commission (the "SEC") and is incorporated by reference in its entirety into this Prospectus Supplement and the accompanying Prospectus. This Prospectus Supplement, the accompanying Prospectus and the SAI are part of a "shelf" registration statement that we filed with the SEC. This Prospectus Supplement describes the specific details regarding this offering, including the method of distribution. If information in this Prospectus Supplement is inconsistent with the accompanying Prospectus or the SAI, you should rely on this Prospectus Supplement. You may request a free copy of the SAI, the table of contents of which is on page 54 of the accompanying Prospectus, a free copy of our annual and semi-annual reports to shareholders, obtain other information or make shareholder inquiries, by calling toll-free 1-800-262-1122 or by writing to the Fund at Two International Place, Boston, Massachusetts 02110. The Fund's SAI and annual and semi-annual reports also are available free of charge on our website athttp://www.eatonvance.comand on the SEC's website (http://www.sec.gov). You may also obtain these documents, after paying a duplication fee, by electronic request at the following email address:[e-mail].

Our securities do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

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TABLE OF CONTENTS

You should rely only on the information contained in, or incorporated by reference into, this Prospectus Supplement and the accompanying Prospectus in making your investment decisions. The Fund has not authorized any person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. The Fund is not making an offer to sell the securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information in this Prospectus Supplement and the accompanying Prospectus is accurate only as of the dates on their covers. The Fund's business, financial condition and prospects may have changed since the date of its description in this Prospectus Supplement or the date of its description in the accompanying Prospectus.

Prospectus Supplement

Prospectus Supplement Summary ................................................ 1

Capitalization ............................................................................. 2

Summary of Fund Expenses ........................................................ 3

Market and Net Asset Value Information ........................................ 4

Use of Proceeds ......................................................................... 5

Plan of Distribution ..................................................................... 6

Legal Matters ............................................................................. 6

Available Information .................................................................. 7

Prospectus

Prospectus Summary ..................................................................... 6

Summary of Fund Expenses ........................................................... 21

Financial Highlights and Investment Performance .............................. 22

The Fund ..................................................................................... 24

Use of Proceeds ............................................................................ 25

Investment Objectives, Policies and Risks ......................................... 25

Management of the Fund ............................................................... 42

Plan of Distribution ........................................................................ 43

Distributions ................................................................................. 44

Federal Income Tax Matters ............................................................ 45

Dividend Reinvestment Plan ........................................................... 48

Description of Capital Structure ....................................................... 49

Custodian and Transfer Agent ......................................................... 53

Legal Opinions .............................................................................. 53

Reports to Shareholders ................................................................. 53

Independent Registered Public Accounting Firm ................................ 53

Additional Information .................................................................... 53

Table of Contents for the Statement of Additional Information .............. 54

The Fund's Privacy Policy ............................................................... 55

Until March 16, 2021 (25 days after the date of this Prospectus Supplement), all dealers that buy, sell or trade the Common Shares, whether or not participating in this offering, may be required to deliver the Prospectus and this Prospectus Supplement. This requirement is in addition to the dealers' obligation to deliver the Prospectus and this Prospectus Supplement when acting as underwriters and with respect to their unsold allotments or subscriptions.

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CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This Prospectus Supplement, the accompanying Prospectus and the SAI contain "forward-looking statements." Forward-looking statements can be identified by the words "may," "will," "intend," "expect," "estimate," "continue," "plan," "anticipate," and similar terms and the negative of such terms. Such forward-looking statements may be contained in this Prospectus Supplement as well as in the accompanying Prospectus. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the SEC.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the "Investment Objectives, Policies and Risks" section of the accompanying Prospectus. All forward-looking statements contained or incorporated by reference in this Prospectus Supplement or the accompanying Prospectus are made as of the date of this Prospectus Supplement or the accompanying Prospectus, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement. The forward-looking statements contained in this Prospectus Supplement, the accompanying Prospectus and the SAI are excluded from the safe harbor protection provided by section 27A of the 1933 Act.

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the "Investment Objectives, Policies and Risks" section of the accompanying Prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

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