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) August 28, 2008

WASHINGTON REAL ESTATE INVESTMENT TRUST

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code (301) 984-9400

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:

Item 1.01 Entry into a Material Definitive Agreement

On August 28, 2008, Washington Real Estate Investment Trust (“WRIT”) entered into a Sales Agency Financing Agreement (“Agreement”) with BNY Mellon Capital Markets, LLC (BNYMCM). Under the terms of the Agreement, WRIT may offer and sell up to $150 million of common shares of beneficial interest, from time to time (“Shares”), and for a period of no more than 36 months. BNYMCM will act as WRIT’s agent in connection with any offerings of shares under the Agreement. The Shares may be offered in one or more selling periods, none of which will exceed 20 trading days. Any Shares sold under the Agreement will be offered at market prices prevailing at the time of sale. WRIT will specify to BNYMCM (i) the aggregate selling price of the Shares to be sold during each selling period, which may not exceed $40,000,000 without BNYMCM’s prior written consent and (ii) the minimum price below which sales may not be made, which may not be less than $1.00 per share without BNYMCM’s prior written consent. WRIT will pay BNYMCM a commission equal to 1% of the sales price of all Shares sold through it as agent under the Agreement plus its reasonable documented out-of-pocket expenses, including fees and expenses of counsel up to $60,000 in aggregate, in connection with the Agreement. In addition, WRIT will pay, during the term of the Agreement, fees of counsel to BNYMCM in connection with its continuing due diligence, in an amount not to exceed $10,000 per fiscal quarter.

The Shares will be issued pursuant to WRIT’s registration statement (Registration Statement) on Form S-3 (File No. 333-136921). WRIT will file a prospectus and prospectus supplement with the Securities and Exchange Commission in connection with the offer and sale of Shares.

The Agreement is filed as Exhibit 1.1 to this Current Report on Form 8-K. The description of the material terms of the Agreement is qualified in its entirety by reference to the exhibit.

Item 9.01 Financial Statements and Exhibits

(c) Exhibits

The following exhibits are filed with this report on Form 8-K:

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

August 28, 2008

Exhibit Index