EXHIBIT 5.1

June 16, 2014

Cellectar Biosciences, Inc.

3301 Agriculture Drive

Madison, WI 53716

Ladies and Gentlemen:

We have acted as counsel to Cellectar Biosciences, Inc., a Delaware corporation (the “Company”), in connection with the filing of a Registration Statement on Form S-1, Registration No. 333-196091 (as amended or supplemented to date, the “Registration Statement”), under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement covers the proposed public offering of up to $20,000,000 in units consisting of a to be determined number of shares of the Company’s common stock, $0.00001 par value per share (“Common Stock”) to be issued directly (such shares of Common Stock, the “Shares”), warrants (the “Warrants”) representing rights to purchase an additional shares of Common Stock in an amount equal to the number of the Shares (the “Warrant Shares”), and the issuance of the Warrant Shares upon exercise of the Warrants. The Shares, the Warrants and the Warrant Shares are collectively referred to herein as the “Securities”.

In rendering the opinions set forth below, we have assumed that (i) all information contained in all documents reviewed by us is true and correct; (ii) all signatures on all documents examined by us are genuine; (iii) all documents submitted to us as originals are authentic, and all documents submitted to us as copies conform to the originals of those documents; (iv) each natural person signing any document reviewed by us had the legal capacity to do so; and (v) the certificates or other documents representing the Securities will be duly executed and delivered.

We express no opinion as to the laws of any state or jurisdiction other than the General Corporation Law of the State of Delaware (including applicable provisions of the Delaware Constitution and reported judicial decisions interpreting such Law and such Constitution), the laws of The Commonwealth of Massachusetts and the federal laws of the United States of America.

We have examined the Registration Statement, including the exhibits thereto, and such other documents, corporate records, and instruments and have examined such laws and regulations as we have deemed necessary for purposes of rendering the opinions set forth herein.

Cellectar Biosciences, Inc.
June 16, 2014

Page 2

Based upon such examination and subject to the further provisions hereof, we are of the following opinion:

The foregoing opinions are qualified to the extent that the enforceability of any document, instrument or the Securities may be limited by or subject to bankruptcy, insolvency, fraudulent transfer or conveyance, reorganization, moratorium or other similar laws relating to or affecting creditors’ rights generally, and general equitable or public policy principles.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and the reference to us under the caption “Legal Matters” in the prospectus included in the Registration Statement. In giving this consent, we do not admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Securities and Exchange Commission promulgated thereunder.

This opinion letter is given to you solely for use in connection with the offer and sale of the Securities while the Registration Statement is in effect and is not to be relied upon for any other purpose. Our opinion is expressly limited to the matters set forth above, and we render no opinion, whether by implication or otherwise, as to any other matters relating to the Company, the Securities or the Registration Statement.