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): March 8, 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 is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

The information set forth in Item 2.03 is incorporated herein by reference.

On March 5, 2013, McKesson Corporation (the “Company”) entered into an Underwriting Agreement (the “Underwriting Agreement”) with J.P. Morgan Securities LLC and Merrill Lynch, Pierce, Fenner & Smith Incorporated, as representatives of the several underwriters named therein (the “Underwriters”), pursuant to which the Company agreed to issue and sell to the Underwriters $500 million aggregate principal amount of its 1.40% Notes due 2018 (the “2018 Notes”) and $400 million aggregate principal amount of its 2.85% Notes due 2023 (the “2023 Notes” and, together with the 2018 Notes, the “Notes”). The Notes will be issued pursuant to the Indenture, dated as of December 4, 2012 (the “Indenture”), between the Company and Wells Fargo Bank, National Association, as trustee (the “Trustee”), as supplemented by an Officers’ Certificate, dated as of March 8, 2013 (the “Officers’ Certificate”).

The 2018 Notes will bear interest at the rate of 1.40% per year. The 2023 Notes will bear interest at the rate of 2.85% per year. Interest on the Notes is payable on March 15 and September 15 of each year, beginning on September 15, 2013. The 2018 Notes will mature on March 15, 2018 and the 2023 Notes will mature on March 15, 2023. Upon 30 days’ notice to holders of the Notes, the Company may redeem the Notes for cash in whole, at any time, or in part, from time to time, prior to maturity, at redemption prices that include accrued and unpaid interest and a make-whole premium, as specified in the Indenture and the Officers’ Certificate. However, no make whole premium will be paid for redemptions of the 2023 Notes on or after December 15, 2022. The Indenture and the Officers’ Certificate include certain covenants, including limitations on the Company’s ability to create certain liens on its assets or enter into sale and leaseback transactions with respect to its properties, or consolidate, merge or sell all or substantially all of its assets, subject to a number of important exceptions as specified in the Indenture. The Notes will be unsecured and unsubordinated obligations of the Company and will rank equally with all of the Company’s existing and future unsecured and unsubordinated indebtedness from time to time outstanding. The Indenture also contains customary event of default provisions. In the event of the occurrence of both (1) a change of control of the Company and (2) a downgrade of a series of Notes below an investment grade rating by each of Fitch Inc., Moody’s Investors Service, Inc. and Standard & Poor’s Ratings Services within a specified period, unless the Company has previously exercised its optional redemption right with respect to that series of Notes in whole, the Company will be required to offer to repurchase the Notes of that series from the holders at a price in cash equal to 101% of the then outstanding principal amount of such series of Notes, plus accrued and unpaid interest to, but not including, the date of repurchase.

The public offering price of the 2018 Notes was 99.797% of the principal amount, and the public offering price of the 2023 Notes was 99.878% of the principal amount. The Company expects to receive net proceeds of approximately $891 million, after deducting underwriting discounts and estimated offering expenses. The Company intends to use the net proceeds from the sale of the Notes for general corporate purposes, including the repayment of borrowings outstanding under the Senior Bridge Term Loan, dated as of December 21, 2012, among the Company, Bank of America, N.A., as administrative agent, and the lenders party thereto.

The Notes were offered and sold pursuant to the Company’s automatic shelf registration statement on Form S-3 (Registration No. 333-179879) under the Securities Act of 1933, as amended. The Company has filed with the Securities and Exchange Commission (the “SEC”) a prospectus supplement, dated March 5, 2013, together with the accompanying prospectus, dated March 2, 2012, relating to the offering and sale of the Notes.

For a complete description of the terms and conditions of the Underwriting Agreement, the Indenture, the Officers’ Certificate and the Notes, please refer to the Underwriting Agreement, the Indenture, the Officers’ Certificate, the form of 2018 Note and the form of 2023 Note, each of which is incorporated herein by reference and attached to this Current Report on Form 8-K as Exhibits 1.1, 4.1, 4.2, 4.3 and 4.4, respectively.

In reviewing the agreements included as exhibits to this Current Report on Form 8-K, please remember they are included to provide you with information regarding their terms and are not intended to provide any other factual or disclosure information about the Company or the other parties to the agreements. The agreements may contain representations and warranties by each of the parties to the applicable agreement. These representations and warranties have been made solely for the benefit of the other parties to the applicable agreement and:

Accordingly, these representations and warranties may not describe the actual state of affairs as of the date they were made or at any other time. Additional information about the Company may be found elsewhere in this Current Report on Form 8-K and our other public filings, which are available without charge through the SEC’s website at http://www.sec.gov.

From time to time in the ordinary course of their respective businesses, certain of the Underwriters, the Trustees and their respective affiliates have engaged in and may in the future engage in commercial banking, derivatives and/or financial advisory, investment banking and other commercial transactions and services with the Company and its affiliates for which they have received or will receive customary fees and commissions.

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 hereunto duly authorized.

Date: March 8, 2013

EXHIBIT INDEX