Exhibit 5.1

[CARDINAL HEALTH, INC. LETTERHEAD]

August 22, 2012

Board of Directors

Cardinal Health, Inc.

7000 Cardinal Place

Dublin, Ohio 43107

Re: Registration Statement on Form S-8 filed by Cardinal Health, Inc.

Ladies and Gentlemen:

I am Vice President and Associate General Counsel of Cardinal Health, Inc., an Ohio corporation (the “Company”). I have acted as counsel to the Company in connection with the Company’s Registration Statement on Form S-8 (the “Registration Statement”) filed under the Securities Act of 1933, as amended (the “Act”), relating to: (a) the registration of 60,000 common shares, without par value (the “Common Shares”), of the Company issuable pursuant to the Cardinal Health Deferred Compensation Plan, as amended and restated effective January 1, 2009 (as amended) (the “DCP”), (b) the registration of 4,000,000 Common Shares issuable pursuant to the Cardinal Health 401(k) Savings Plan, as amended and restated effective January 1, 2011 (as amended) (collectively with the DCP, the “Plans”), and (c) registration of up to $40,000,000 in aggregate value of deferred compensation obligations (the “Obligations”), which represent unsecured obligations of the Company to pay deferred compensation to eligible participants in the future in accordance with the terms of the DCP.

In rendering this opinion, I have examined such documents and records, including an examination of originals or copies certified or otherwise identified to my satisfaction, and matters of law as I have deemed relevant or necessary for purposes of this opinion.

Based on the foregoing, and subject to the further qualifications, assumptions and limitations stated herein, I am of the opinion that (i) the Common Shares that may be issued or delivered and sold pursuant to the Plans have been authorized by all necessary corporate action of the Company and will be, when issued or delivered and sold in accordance with such Plans, validly issued, fully paid and nonassessable and (ii) upon completion of the actions being taken or contemplated by me as Company counsel to be taken in administering the DCP, the Obligations will constitute valid and binding obligations of the Company, enforceable in accordance with their terms.

My examination, or the examination by attorneys under my supervision, of matters of law in connection with the opinions expressed herein has been limited to, and accordingly my opinions herein are limited to, the laws of the State of Ohio, as currently in effect. I express no opinion as to the effect of the laws of any other jurisdiction. In addition, I have assumed that the resolutions authorizing the Company to issue or deliver and sell the Common Shares pursuant to the Plans and to issue the Obligations in accordance with the DCP will be in full force and effect at all times at which such Common Shares are issued or delivered and sold by the Company or at which such Obligations are issued, and the Company will take no action inconsistent with such resolutions. The opinion set forth above is limited by bankruptcy, insolvency, reorganization, fraudulent transfer and fraudulent conveyance, voidable preference, moratorium or other similar laws and related regulations and judicial doctrines from time to time in effect relating to or affecting creditors’ rights generally, and by general equitable principles and public policy considerations, whether such principles and considerations are considered in a proceeding at law or at equity.

I hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement filed by the Company to effect registration of the Common Shares to be issued or delivered and sold pursuant to the Plans and the Obligations to be issued pursuant to the DCP under the Act. In giving such consent, I do not thereby admit that I am in the category of person whose consent is required under Section 7 of the Act or the rules and regulations of the U.S. Securities and Exchange Commission.

Very truly yours,

/s/ JAMES E. BARNETT

James E. Barnett

Vice President and Associate

General Counsel