Exhibit 5.1

		Hogan Lovells US LLP Columbia Square 555 Thirteenth Street, NW Washington, DC 20004 T +1 202 637 5600 F +1 202 637 5910 www.hoganlovells.com

March 8, 2018

Board of Trustees

Washington Real Estate Investment Trust

1775 Eye Street, NW

Suite 100

Washington, DC 20006

Ladies and Gentlemen:

We are acting as counsel to Washington Real Estate Investment Trust, a Maryland real estate investment trust (the “Company”), in connection with its registration statement on Form S-3, as amended (the “Registration Statement”), filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Act”) relating to the resale from time to time by the selling shareholders identified in the Registration Statement of up to 12,124 common shares of beneficial interest, par value $0.01 per share, of the Company (the “Shares”). This opinion letter is furnished to you at your request to enable you to fulfill the requirements of Item 601(b)(5) of Regulation S-K, 17 C.F.R. § 229.601(b)(5), in connection with the Registration Statement.

For purposes of this opinion letter, we have examined copies of such agreements, instruments and documents as we have deemed an appropriate basis on which to render the opinions hereinafter expressed. In our examination of the aforesaid documents, we have assumed the genuineness of all signatures, the legal capacity of all natural persons, the accuracy and completeness of all documents submitted to us, the authenticity of all original documents, and the conformity to authentic original documents of all documents submitted to us as copies (including pdfs). We also have assumed that the Shares will not be issued in violation of the ownership limit contained in the Company’s Articles of Amendment and Restatement, as amended (the “Declaration of Trust”). As to all matters of fact, we have relied on the representations and statements of fact made in the documents so reviewed, and we have not independently established the facts so relied on. This opinion letter is given, and all statements herein are made, in the context of the foregoing.

This opinion letter is based as to matters of law solely on Maryland General Corporation Law, as amended. We express no opinion herein as to any other statutes, rules or regulations.

Based upon, subject to and limited by the foregoing, we are of the opinion that, the Shares, if and when issued in accordance with the terms of the Amended and Restated Agreement of Limited Partnership of WashREIT Watergate 600 OP LP, dated as of April 4, 2017, will be validly issued, fully paid, and nonassessable.

This opinion letter has been prepared for use in connection with the Registration Statement. We assume no obligation to advise of any changes in the foregoing subsequent to the effective date of the Registration Statement.

We hereby consent to the filing of this opinion letter as Exhibit 5.1 to the Registration Statement and to the reference to this firm under the caption “Legal Matters” in the prospectus constituting a part of the Registration Statement. In giving this consent, we do not thereby admit that we are an “expert” within the meaning of the Act.