UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): November 13, 2013

McKesson Corporation

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (415) 983-8300

Not Applicable

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

On November 15, 2013, McKesson Corporation (the “Company”) entered into Amendment No. 1 (the “Credit Agreement Amendment”) to its syndicated $1.3 billion five-year senior unsecured Credit Agreement, dated as of September 23, 2011 (the “Credit Agreement”), with McKesson Canada Corporation, as co-borrower, Bank of America, N.A., as administrative agent, Bank of America, N.A. (acting through its Canada branch), as Canadian administrative agent, and the lenders party thereto. The Credit Agreement Amendment increased the maximum debt to capital ratio covenant from 56.5% to 65%. The Credit Agreement Amendment also added a cure period with respect to defaults under the Credit Agreement relating to Celesio AG (“Celesio”) or any of its subsidiaries. The cure period allows the Company to remedy any default during the period beginning on the closing date of the Bridge Term Loan Agreement, dated as of October 23, 2013 (the “Bridge Loan Agreement”), and ending on the later of (i) 90 days from and including such closing date and (ii) 60 days following the discovery by a responsible officer of the Company of such default.

On November 15, 2013, the Company entered into Amendment No. 3 (the “Receivables Purchase Agreement Amendment”) to its Fourth Amended and Restated Receivables Purchase Agreement, dated as of May 18, 2011 (the “Receivables Purchase Agreement”), with CGSF Funding Corporation, as seller, the conduit purchasers party thereto, the committed purchasers party thereto, the managing agents party thereto and The Bank of Tokyo-Mitsubishi UFJ, Ltd., New York Branch (as successor to JPMorgan Chase Bank, N.A.), as collateral agent. The Receivables Purchase Agreement Amendment increased the maximum debt to capital ratio covenant from 56.5% to 65%. The Receivables Purchase Agreement Amendment also added a cure period with respect to defaults under the Credit Agreement relating to Celesio or any of its subsidiaries, which is substantially similar to the cure period provided by the Credit Agreement Amendment, as discussed above. Additionally, the Receivables Purchase Agreement Amendment, among certain other modifications, extended the facility termination date from November 15, 2013 to November 14, 2014.

The above descriptions of the Credit Agreement Amendment and Receivables Purchase Agreement Amendment do not purport to be complete and are qualified in their entirety by reference to the executed copies of the amendments and agreements, attached hereto as Exhibits 10.1 and 10.2, respectively, which are incorporated herein by reference.

On November 13, 2013, the Company entered into Amendment No. 1 to its $5.5 billion 364-day unsecured Bridge Loan Agreement, with Bank of America, N.A., as administrative agent, and the lenders party thereto, to clarify a closing condition regarding the requirement to provide certain financial statements of Celesio.

The foregoing description of the amendment to the Bridge Loan Agreement does not purport to be complete and is qualified in its entirety by reference to the executed copy of the amendment and Bridge Loan Agreement, attached hereto as Exhibit 10.3, which is incorporated herein by reference.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

EXHIBIT INDEX