Exhibit 5.1

Quintiles Transnational Holdings Inc.

4820 Emperor Blvd.

Durham, North Carolina 27703

Ladies and Gentlemen:

We have acted as counsel for Quintiles Transnational Holdings Inc., a North Carolina corporation (the “Company”), in connection with the Registration Statement on Form S-1 (the “Registration Statement”) filed on the date hereof with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), relating to the sale by the selling shareholders identified in the Registration Statement (the “Selling Shareholders”) of up to 17,250,000 shares of the Company’s common stock, par value $0.01 per share (“Common Stock”) (the “Shares”).

This opinion is furnished in accordance with the requirements of Item 601(b)(5)(i) of Regulation S-K under the Act.

We have reviewed such documents and considered such matters of law and fact as we, in our professional judgment, have deemed appropriate to render the opinions contained herein. With respect to certain facts, we have considered it appropriate to rely upon certificates or other comparable documents of public officials and officers or other appropriate representatives of the Company, without investigation or analysis of any underlying data contained therein.

Based upon and subject to the foregoing and in reliance thereon and subject to the qualifications, assumptions and limitations stated herein, it is our opinion that the Shares have been duly authorized and are validly issued, fully paid and nonassessable.

We express no opinion as to any matter other than as expressly set forth above, and no opinion, other than the opinion given herein, may be inferred or implied herefrom. This opinion is limited to the laws of the State of North Carolina and we express no opinion as to the laws of any other jurisdiction. The opinion expressed herein does not extend to compliance with federal or state securities laws relating to the sale of the Shares.

Our opinion is as of the date hereof, and we do not undertake to advise you of matters that might come to our attention subsequent to the date hereof which may affect our legal opinion expressed herein.

We consent to the filing of this opinion as an exhibit to the Registration Statement and to all references to us in the Registration Statement, including the prospectus and any amendment or supplement thereto. Such consent shall not be deemed to be an admission that our firm is within the category of persons whose consent is required under Section 7 of the Act or the regulations promulgated pursuant to the Act.