SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K/A1

Amendment No. 1

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported) March 9, 2007

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:

The undersigned registrant, in order to provide the financial statements required to be included in the Current Report on Form 8-K dated March 9, 2007 in connection with the acquisition of certain assets and the borrowing under the lines of credit to pay for the acquisitions of 270 Technology Park, Monument II and 2440 M Street hereby amends the following items, as set forth in the pages attached hereto.

In acquiring the properties listed above, Washington Real Estate Investment Trust (“WRIT”) evaluated among other things, sources of revenue (including but not limited to, competition in the rental market, comparative rents and occupancy rates) and expenses (including but not limited to, utility rates, ad valorem tax rates, maintenance expenses and anticipated capital expenditures). After reasonable inquiry, management is not aware of any material factors affecting these properties that would cause the reported financial information not to be indicative of their future operating results.

The following pro forma financial statements for the property acquisitions listed above (as defined in Regulation S-X) are filed as an exhibit hereto:

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.

May 25, 2007

(Date)

REPORT OF INDEPENDENT ACCOUNTANTS

To the Board of Trustees of

  Washington Real Estate Investment Trust

We have audited the accompanying Historical Summary of Gross Income and Direct Operating Expenses of 270 Technology Park (“Historical Summary”) for the year ended December 31, 2006. This Historical Summary is the responsibility of the Property’s management. Our responsibility is to express an opinion on the Historical Summary based on our audit.

We conducted our audit in accordance with auditing standards generally accepted in the United States of America. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the Historical Summary is free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the Historical Summary. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the Historical Summary. We believe that our audit provides a reasonable basis for our opinion.

The accompanying Historical Summary was prepared for the purpose of complying with the rules and regulations of the Securities and Exchange Commission as described in Note 2, and is not intended to be a complete presentation of 270 Technology Park’s revenues and expenses.

In our opinion, the Historical Summary referred to above presents fairly, in all material respects, the gross income and direct operating expenses described in Note 2 of 270 Technology Park for the year ended December 31, 2006, in conformity with accounting principles generally accepted in the United States of America.

/s/ ARGY, WILTSE & ROBINSON, P.C.

McLean, Virginia

May 17, 2007

270 TECHNOLOGY PARK

HISTORICAL SUMMARY OF GROSS INCOME AND DIRECT OPERATING EXPENSES

YEAR ENDED DECEMBER 31, 2006

The accompanying notes are an integral part of this historical summary.

270 TECHNOLOGY PARK

NOTES TO THE HISTORICAL SUMMARY OF GROSS INCOME AND

DIRECT OPERATING EXPENSES

YEAR ENDED DECEMBER 31, 2006

NOTE 1 - NATURE OF BUSINESS

270 Technology Park consists of five single-story flex buildings containing a total of approximately 157,000 rentable square feet plus 595 parking spaces, located within 270 Technology Park in Frederick, Maryland. The operations of 270 Technology Park consist of leasing space to various business tenants.

NOTE 2 - BASIS OF PRESENTATION

Washington Real Estate Investment Trust purchased 270 Technology Park in February, 2007. The Historical Summary has been prepared for the purpose of complying with Regulation S-X, Rule 3-14 of the Securities and Exchange Commission (“SEC”), which requires certain information with respect to real estate operations acquired to be included with certain filings with the SEC. This Historical Summary includes the historical gross income and direct operating expenses of 270 Technology Park, exclusive of the following expenses which may not be comparable to the proposed future operations:

NOTE 3 - USE OF ESTIMATES

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions regarding revenues and expenses. Such estimates primarily relate to unsettled transactions and events as of the date of the financial statements. Accordingly, upon settlement, actual results could differ from estimated amounts.

NOTE 4 - DESCRIPTION OF LEASING ARRANGEMENTS

All leases are classified as operating leases and expire at various dates through 2016. The following is a schedule by years of future minimum rents receivable on non-cancelable operating leases in effect as of December 31, 2006:

During the year ended December 31, 2006, three tenants accounted for approximately 35% of the total base rents.

REPORT OF INDEPENDENT ACCOUNTANTS

To the Board of Trustees of

  Washington Real Estate Investment Trust

We have audited the accompanying Historical Summary of Gross Income and Direct Operating Expenses of Monument II (“Historical Summary”) for the year ended December 31, 2006. This Historical Summary is the responsibility of the Property’s management. Our responsibility is to express an opinion on the Historical Summary based on our audit.

We conducted our audit in accordance with auditing standards generally accepted in the United States of America. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the Historical Summary is free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the Historical Summary. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the Historical Summary. We believe that our audit provides a reasonable basis for our opinion.

The accompanying Historical Summary was prepared for the purpose of complying with the rules and regulations of the Securities and Exchange Commission as described in Note 2, and is not intended to be a complete presentation of Monument II’s revenues and expenses.

In our opinion, the Historical Summary referred to above presents fairly, in all material respects, the gross income and direct operating expenses described in Note 2 of Monument II for the year ended December 31, 2006, in conformity with accounting principles generally accepted in the United States of America.

/s/ ARGY, WILTSE & ROBINSON, P.C.

McLean, Virginia

May 17, 2007

MONUMENT II

HISTORICAL SUMMARY OF GROSS INCOME AND DIRECT OPERATING EXPENSES

YEAR ENDED DECEMBER 31, 2006

The accompanying notes are an integral part of this historical summary.

MONUMENT II

NOTES TO THE HISTORICAL SUMMARY OF GROSS INCOME AND

DIRECT OPERATING EXPENSES

YEAR ENDED DECEMBER 31, 2006

NOTE 1 - NATURE OF BUSINESS

Monument II is a class A, 205,000 square foot, eight-story building with a five-level parking garage located in Herndon, Virginia. The operations of Monument II consist of leasing offices to various business tenants.

NOTE 2 - BASIS OF PRESENTATION

Washington Real Estate Investment Trust purchased Monument II in March, 2007. The Historical Summary has been prepared for the purpose of complying with Regulation S-X, Rule 3-14 of the Securities and Exchange Commission (“SEC”), which requires certain information with respect to real estate operations acquired to be included with certain filings with the SEC. This Historical Summary includes the historical gross income and direct operating expenses of Monument II, exclusive of the following expenses which may not be comparable to the proposed future operations:

NOTE 3 - USE OF ESTIMATES

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions regarding revenues and expenses. Such estimates primarily relate to unsettled transactions and events as of the date of the financial statements. Accordingly, upon settlement, actual results could differ from estimated amounts.

NOTE 4 - DESCRIPTION OF LEASING ARRANGEMENTS

All leases are classified as operating leases and expire at various dates through 2011. The following is a schedule by years of future minimum rents receivable on non-cancelable operating leases in effect as of December 31, 2006:

During the year ended December 31, 2006, three tenants accounted for approximately 80% of the total base rents.

REPORT OF INDEPENDENT ACCOUNTANTS

To the Board of Trustees of

  Washington Real Estate Investment Trust

We have audited the accompanying Historical Summary of Gross Income and Direct Operating Expenses of 2440 M Street (“Historical Summary”) for the year ended December 31, 2006. This Historical Summary is the responsibility of the Property’s management. Our responsibility is to express an opinion on the Historical Summary based on our audit.

We conducted our audit in accordance with auditing standards generally accepted in the United States of America. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the Historical Summary is free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the Historical Summary. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the Historical Summary. We believe that our audit provides a reasonable basis for our opinion.

The accompanying Historical Summary was prepared for the purpose of complying with the rules and regulations of the Securities and Exchange Commission as described in Note 2, and is not intended to be a complete presentation of 2440 M Street’s revenues and expenses.

In our opinion, the Historical Summary referred to above presents fairly, in all material respects, the gross income and direct operating expenses described in Note 2 of 2440 M Street for the year ended December 31, 2006, in conformity with accounting principles generally accepted in the United States of America.

/s/ ARGY, WILTSE & ROBINSON, P.C.

McLean, Virginia

May 17, 2007

2440 M STREET

HISTORICAL SUMMARY OF GROSS INCOME AND DIRECT OPERATING EXPENSES

YEAR ENDED DECEMBER 31, 2006

The accompanying notes are an integral part of this historical summary.

2440 M STREET

NOTES TO THE HISTORICAL SUMMARY OF GROSS INCOME AND

DIRECT OPERATING EXPENSES

YEAR ENDED DECEMBER 31, 2006

NOTE 1 - NATURE OF BUSINESS

2440 M Street is a class A, 110,000 square foot medical office building with a three-level parking garage in northwest Washington, D.C. The operations of 2440 M Street consist of leasing offices primarily to medical related tenants.

NOTE 2 - BASIS OF PRESENTATION

Washington Real Estate Investment Trust purchased 2440 M Street in March, 2007. The Historical Summary has been prepared for the purpose of complying with Regulation S-X, Rule 3-14 of the Securities and Exchange Commission (“SEC”), which requires certain information with respect to real estate operations acquired to be included with certain filings with the SEC. This Historical Summary includes the historical gross income and direct operating expenses of 2440 M Street, exclusive of the following expenses which may not be comparable to the proposed future operations:

NOTE 3 - USE OF ESTIMATES

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions regarding revenues and expenses. Such estimates primarily relate to unsettled transactions and events as of the date of the financial statements. Accordingly, upon settlement, actual results could differ from estimated amounts.

NOTE 4 - DESCRIPTION OF LEASING ARRANGEMENTS

All leases are classified as operating leases and expire at various dates through 2019. The following is a schedule by years of future minimum rents receivable on non-cancelable operating leases in effect as of December 31, 2006:

WASHINGTON REAL ESTATE INVESTMENT TRUST

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET AND

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

The pro forma balance sheet as of December 31, 2006 presents consolidated financial information as if the acquisitions had taken place on December 31, 2006. The pro forma statements of operations for the year ended December 31, 2006 present the pro forma results of operations as if the acquisitions had taken place as of the beginning of the reporting period. Both the balance sheets and statements of operations illustrate the operating results of each of the properties acquired as well as compilation of the pro forma adjustments that were necessary to develop the pro forma results for the registrant. Explanations or details of the pro forma adjustments are in the notes to each of the financial statements.

WRIT purchased these properties as follows during 2007:

The unaudited consolidated pro forma financial information is not necessarily indicative of what WRIT’s actual results of operations or financial position would have been had these transactions been consummated on the dates indicated, nor does it purport to represent WRIT’s results of operations or financial position for any future period. The results of operations for the period ended December 31, 2006 are not necessarily indicative of the operating results for the period.

The unaudited consolidated pro forma financial information should be read in conjunction with WRIT’s Form 8-K filed with the Securities and Exchange Commission (“SEC”) on March 9, 2007, announcing the acquisitions; the consolidated financial statements and notes thereto included in WRIT’s Annual Report on Form 10-K for the year ended December 31, 2006; and the Historical Summary of Gross Income and Direct Operating Expenses and Notes included elsewhere in this Form 8-K/A1. In management’s opinion, all adjustments necessary to reflect these acquisitions and related transactions have been made.

WASHINGTON REAL ESTATE INVESTMENT TRUST

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET

DECEMBER 31, 2006

(In thousands)

WASHINGTON REAL ESTATE INVESTMENT TRUST

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET

DECEMBER 31, 2006

(In thousands, except per share amounts)

NOTES TO PRO FORMA BALANCE SHEET

Note 1: WRIT accounted for the acquisitions using the purchase method of accounting. WRIT allocated the purchase price to the related physical assets (land, building and tenant improvements) and in-place leases (tenant origination costs, leasing commissions and absorption costs, and net lease intangible assets/liabilities) based on their fair values, in accordance with SFAS No. 141, “Business Combinations.”

Note 2: Adjustments to the Pro Forma Condensed Consolidated Balance Sheet represent funds raised through an equity offering, draws on the line of credit, cash paid and deposits applied at closing, and the assumption of certain assets and liabilities, including real estate and personal property taxes and security deposits.

Acquisition related borrowings on our credit facilities totaled $79.2 million. This was to fund $30 million of the purchase price for Monument II and $49.2 for the purchase of 2440 M Street. Advances under this agreement bear interest at WRIT’s option of LIBOR plus a spread based on the credit rating on our publicly issued debt or the higher of Wells Fargo Bank’s prime rate and the Federal Funds Rate in effect on that day plus 0.5%. All outstanding advances are due and payable upon maturity in November 2010.

WASHINGTON REAL ESTATE INVESTMENT TRUST

UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS

FOR THE YEAR ENDED DECEMBER 31, 2006

(In thousands, except per share amounts)

NOTES TO PRO FORMA STATEMENT OF OPERATIONS