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 25, 2014

TESORO LOGISTICS LP

(Exact name of registrant as specified in its charter)

(210) 626-6000

(Registrant’s telephone number, including area code)

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 (see General Instruction A.2.):

Item 1.01 Entry into a Material Definitive Agreement.

Equity Distribution Agreement

On June 25, 2014, Tesoro Logistics LP (the “Partnership”) and Tesoro Logistics GP, LLC, the general partner of the Partnership (the “General Partner”), entered into an Equity Distribution Agreement (the “Agreement”) with Citigroup Global Markets Inc. (the “Manager”). Pursuant to the terms of the Agreement, the Partnership may sell from time to time through the Manager, as the Partnership’s sales agent, common units representing limited partner interests in the Partnership having an aggregate offering price of up to $200,000,000 (the “Common Units”). Sales of the Common Units, if any, will be made by means of ordinary brokers’ transactions on the New York Stock Exchange at market prices or as otherwise agreed by the Partnership and the Manager.

Under the terms of the Agreement, the Partnership may also sell Common Units from time to time to the Manager as principal for its own account at a price to be agreed upon at the time of sale. Any sale of Common Units to the Manager as principal would be pursuant to the terms of a separate terms agreement between the Partnership and the Manager.

The Partnership intends to use the net proceeds of any sales pursuant to the Agreement, after deducting the Manager’s commission and offering expenses, for general partnership purposes, which may include, among other things, future acquisitions, repayment of indebtedness, capital expenditures and additions to working capital.

The Common Units will be issued pursuant to the Partnership’s effective Registration Statement on Form S-3 (Registration No. 333-181592).

The Agreement contains customary representations, warranties and agreements of the Partnership and the General Partner, including obligations of the Partnership and the General Partner to indemnify the Manager for certain liabilities under the Securities Act of 1933, as amended, and to contribute to payments the Manager may be required to make because of any of those liabilities. The foregoing description of the Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Agreement, which is filed as Exhibit 1.1 hereto and incorporated by reference herein.

Relationships

The Manager and its affiliates have engaged, and may in the future engage, in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The Manager and its affiliates have performed and may perform investment and commercial banking and advisory services for the Partnership and its affiliates from time to time, for which they have received and may receive customary fees and expense reimbursement. The Manager and its affiliates may, from time to time, engage in transactions with and perform services for the Partnership in the ordinary course of their business. Affiliates of the Manager are lenders under the Partnership’s credit facility.

Item 9.01 Financial Statements and Exhibits.

(d) 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.

Date: June 25, 2014

Index to Exhibits