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): June 17, 2013

NAVISTAR INTERNATIONAL CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (331) 332-5000

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:

Item 1.01. Entry Into A Material Definitive Agreement.

On June 17, 2013, Navistar International Corporation (the “Company”) and Computershare Shareowner Services LLC, as Rights Agent (the “Rights Agent”) under the Rights Agreement, dated as of June 19, 2012, as amended from time to time, between the Company and the Rights Agent (the “Rights Agreement”), entered into Amendment No. 4 to the Rights Agreement (“Amendment No. 4”). Amendment No. 4 amends and restates Section 7(a) of the Rights Agreement in order to extend the expiration date of the Rights Agreement from June 18, 2013 to August 31, 2013.

The foregoing description of Amendment No. 4 does not purport to be complete and is qualified in its entirety by the complete text of Amendment No. 4, a copy of which is filed as Exhibit 4.1 to this Form 8-K and incorporated by reference herein.

Item 3.03. Material Modification to Rights of Security Holders.

The disclosure set forth in Item 1.01 of this Form 8-K is incorporated by reference into this Item 3.03.

Item 9.01. Financial Statements and Exhibits.

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.

EXHIBIT INDEX