Exhibit 5.1

May 17, 2010

Board of Directors

DuPont Fabros Technology, Inc.

1212 New York Avenue, NW, Suite 900

Washington, DC 20005

Ladies and Gentlemen:

We are acting as counsel to DuPont Fabros Technology, Inc., a Maryland corporation (the “Company”), in connection with the public offering of up to 13,800,000 shares of the Company’s common stock, par value $0.001 per share (the “Shares”), all of which Shares are to be sold by the Company pursuant to a prospectus supplement dated May 12, 2010 and the accompanying prospectus dated May 4, 2009 (such documents, collectively, the “Prospectus”) that form part of the Company’s effective registration statement on Form S-3 (File No. 333-158585) (the “Registration Statement”). 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 telecopies). We have also assumed that the Shares will not be issued in violation of the ownership limit contained in the Company’s Articles of Amendment and Restatement of Incorporation. 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.

Board of Directors

DuPont Fabros Technology, Inc.

May 17, 2010

Page 2

This opinion letter is based as to matters of law solely on the applicable provisions of the Maryland General Corporation Law, as amended, currently in effect. We express no opinion herein as to any other laws, statutes, ordinances, rules, or regulations. As used herein, the term “Maryland General Corporation Law, as amended” includes the applicable statutory provisions contained therein, all applicable provisions of the Maryland Constitution and reported judicial decisions interpreting these laws.

Based upon, subject to and limited by the foregoing, we are of the opinion that following (i) issuance and delivery of the Shares pursuant to the terms of the Underwriting Agreement dated May 12, 2010, by and among the Company and KeyBanc Capital Markets Inc. and Raymond James & Associates, Inc., as representatives of the several underwriters listed on Schedule 1 attached thereto, and (ii) receipt by the Company of the consideration for the Shares specified in the resolutions of the Board of Directors and the Pricing Committee of the Board of Directors, the Shares will be validly issued, fully paid, and nonassessable.

This opinion letter has been prepared for use in connection with the filing by the Company of a Current Report on Form 8-K relating to the offer and sale of the Shares, which Form 8-K will be incorporated by reference into the Registration Statement and Prospectus, and speaks as of the date hereof. We assume no obligation to advise you of any changes in the foregoing subsequent to the delivery of this letter.

We hereby consent to the filing of this opinion letter as Exhibit 5.1 to the above-described Form 8-K and to the reference to this firm under the caption “Legal Matters” in the Prospectus. In giving this consent, we do not thereby admit that we are an “expert” within the meaning of the Securities Act of 1933, as amended.