Exhibit 5.1

January 22, 2010   Curis, Inc. 45 Moulton Street Cambridge, MA 02138

Re: Prospectus Supplement to Registration Statement on Form S-3

Ladies and Gentlemen:

This opinion is furnished to you in connection with (i) the Registration Statement on Form S-3 (File No. 333-152612) (as amended, the “Registration Statement”) filed by Curis, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”) for the registration of common stock, par value $0.01 per share (the “Common Stock”), preferred stock and warrants to purchase Common Stock, all of which may be issued from time to time on a delayed or continuous basis pursuant to Rule 415 under the Securities Act at an aggregate initial offering price not to exceed $50,000,000 and (ii) the prospectus supplement, dated January 22, 2010, filed with the Commission pursuant to Rule 424(b) of the Securities Act (the “Prospectus Supplement”) relating to the issue and sale of up to 6,449,288 shares (the “Shares”) of Common Stock, Warrants to purchase up to 1,612,322 shares of Common Stock (the “Warrants”) and the shares of Common Stock issuable upon exercise of the Warrants (the “Warrant Shares” and, together with the Warrants and the Shares, the “Securities”).

The Shares and the Warrants are to be sold by the Company to selected investors pursuant to subscription agreements (the “Subscription Agreements”) in the form attached as Exhibit A to the placement agent agreement (the “Placement Agent Agreement”) by and among the Company, RBC Capital Markets Corporation and Rodman & Renshaw, LLC, dated January 22, 2010, which has been filed as Exhibit 1.1 to the Company’s Current Report on Form 8-K, dated January 22, 2010, as filed with the Commission on the date hereof.

We are acting as counsel for the Company in connection with the issue and sale by the Company of the Securities. We have examined copies of the Registration Statement and the Prospectus Supplement, each as filed with the Commission. We have also examined and relied upon the Placement Agent Agreement and the Subscription Agreements, minutes of meetings of the stockholders and the Board of Directors of the Company, including committees thereof, as provided to us by the Company, the Certificate of Incorporation and By-Laws of the Company, each as restated and/or amended to date, and such other documents as we have deemed necessary for purposes of rendering the opinions hereinafter set forth.

In our examination of the foregoing documents, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as copies, the authenticity of the originals of such latter documents and the legal competence of all signatories to such documents.

Curis, Inc.

January 22, 2010

Page 2

We express no opinion herein as to the laws of any state or jurisdiction other than the state laws of the State of New York and the General Corporation Law of the State of Delaware.

On the basis of and subject to the foregoing, we are of the opinion that:

It is understood that this opinion is to be used only in connection with the offer and sale of the Securities while the Registration Statement is in effect and may not be used, quoted or relied upon for any other purpose nor may this opinion be furnished to, quoted to or relied upon by any other person or entity, for any purpose, without our prior written consent.

Please note that we are opining only as to the matters expressly set forth herein, and no opinion should be inferred as to any other matters. This opinion is based upon currently existing statutes, rules, regulations and judicial decisions, and we disclaim any obligation to advise you of any change in any of these sources of law or subsequent legal or factual developments which might affect any matters or opinions set forth herein.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Company’s Current Report on Form 8-K, dated January 22, 2010, to be filed with the Commission in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act and to the use of our name in the Prospectus Supplement under the caption “Legal Matters.” In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

Curis, Inc.

January 22, 2010

Page 3