UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of The

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): February 28, 2012

DIGITAL REALTY TRUST, INC.

DIGITAL REALTY TRUST, L.P.

(Exact name of registrant as specified in its charter)

(415) 738-6500

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

SUPPLEMENTAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

This discussion is a supplement to, and is intended to be read together with, the discussions under the heading “United States Federal Income Tax Considerations” included in our Registration Statement on Form S-3 (File No. 333-158958 and 333-158958-01) (the “Registration Statement”), and is intended to supersede the discussion under the heading “Supplemental United States Federal Income Tax Considerations” included in our Current Report on Form 8-K filed with the SEC on July 29, 2011. This summary is for general information only and is not tax advice.

The following discussion replaces the discussion under the heading “Tax Rates.”

The maximum tax rate for non-corporate taxpayers for capital gains, including certain “capital gain dividends,” is generally 15% (although depending on the characteristics of the assets which produced these gains and on designations which we may make, certain capital gain dividends may be taxed at a 25% rate). Capital gain dividends will only be eligible for the rates described above to the extent they are properly designated by the REIT as “capital gain dividends.” The maximum tax rate for non-corporate taxpayers for income that the REIT properly designates as “qualified dividend income” is generally 15%. In general, dividends payable by REITs are not eligible for the 15% tax rate on qualified dividend income, except to the extent that the taxpayer satisfies certain holding requirements with respect to the REIT’s stock and the REIT’s dividends are attributable to dividends received from certain taxable corporations (such as its taxable REIT subsidiaries) or to income that was subject to tax at the corporate/REIT level (for example, if the REIT distributed taxable income that it retained and paid tax on in the prior taxable year). For taxable years beginning after December 31, 2012, the 15% capital gains tax rate is currently scheduled to increase to 20% and the rate applicable to dividends is currently scheduled to increase to the tax rate then applicable to ordinary income. In addition, U.S. stockholders that are corporations may be required to treat up to 20% of some capital gain dividends as ordinary income.

Medicare Tax on Unearned Income. Certain U.S. stockholders that are individuals, estates or trusts are required to pay an additional 3.8% tax on, among other things, dividends, interest on and capital gains from the sale or other disposition of stock or debt obligations for taxable years beginning after December 31, 2012. U.S. stockholders should consult their tax advisors regarding the effect, if any, of this additional tax on their ownership and disposition of our capital stock or debt securities.

The following discussion replaces the discussion under the heading “Withholding Taxes on Certain Foreign Accounts” in the Registration Statement.

Withholding taxes may apply to certain types of payments made to “foreign financial institutions” (as specially defined in the Code) and certain other non-United States entities. Specifically, a 30% withholding tax may be imposed on dividends and interest on, and gross proceeds from the sale or other disposition of, our capital stock or debt securities paid to a foreign financial institution or to a non-financial foreign entity, unless (1) the foreign financial institution undertakes certain diligence and reporting, (2) the non-financial foreign entity either certifies it does not have any substantial United States owners or furnishes identifying information regarding each substantial United States owner, or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in clause (1) above, it must enter into an agreement with the United States Treasury requiring, among other things, that it undertake to identify accounts held by certain United States persons or United States-owned foreign entities, annually report certain information about such accounts, and withhold 30% on payments to non-compliant foreign financial institutions and certain other account holders.

Although these rules currently apply to applicable payments made after December 31, 2012 (other than interest payments made on certain debt securities discussed below), the IRS has issued Proposed Treasury Regulations providing that the withholding provisions described above will generally apply to payments of dividends or interest made on or after January 1, 2014 and to payments of gross proceeds from a sale or other disposition of stock or debt securities on or after January 1, 2015. In addition, although these rules currently would not apply to debt securities outstanding on March 18, 2012, the Proposed Treasury Regulations extend the date of their initial application and indicate that this withholding tax would not apply to debt securities issued before January 1, 2013 (and not materially modified after December 31, 2012).

The Proposed Treasury Regulations described above will not be effective until they are issued in their final form, and as of the date of this report, it is not possible to determine whether the proposed regulations will be finalized in their current form or at all. Prospective investors should consult their tax advisors regarding these withholding provisions.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrants have duly caused this report to be signed on their behalf by the undersigned hereunto duly authorized.

Date: February 28, 2012