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): September 15, 2009

NuStar Energy L.P.

(Exact name of registrant as specified in its charter)

Delaware |  | 001-32940 |  | 85-0470977
State or other jurisdiction Of incorporation |  | (Commission File Number) |  | (IRS Employer Identification No.)

2330 North Loop 1604 West San Antonio, Texas |  | 78248
(Address of principal executive offices) |  | (Zip Code)

Registrant’s telephone number, including area code: (210) 918-2000

(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:

¨ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 7.01 Regulation FD Disclosure.

On Wednesday, September 16, 2009, senior management of NuStar Energy L.P. (the “Company”) will make a presentation (the “Presentation”) to investors at the 2009 Master Limited Partnership Investor Conference, sponsored by the National Association of Publicly Traded Partnerships, in Greenwich, Connecticut at 8:00 a.m. (Eastern Time). The slides attached to this report were prepared in connection with the Presentation. The slides are included in Exhibit 99.1 to this report and are incorporated herein by reference. The slides will be available on the Company’s website at www.nustarenergy.com. Additionally, a live audio webcast and replays of the Company’s Presentation will be available beginning at approximately 8:00 a.m. (Eastern Time) on September 16, 2009 on the “Investors” section of its website at www.nustarenergy.com.

The information in this report is being furnished, not filed, pursuant to Regulation FD. Accordingly, the information in Items 7.01 and 9.01 of this report will not be incorporated by reference into any registration statement filed by the Company under the Securities Act of 1933, as amended, unless specifically identified therein as being incorporated therein by reference. The furnishing of the information in this report is not intended to, and does not, constitute a determination or admission by the Company that the information in this report is material or complete, or that investors should consider this information before making an investment decision with respect to any security of the Company or any of its affiliates.

Safe Harbor Statement

Statements contained in the exhibit to this report state the Company’s or its management’s expectations or predictions of the future and are forward-looking statements intended to be covered by the safe harbor provisions of the Securities Act of 1933, as amended, and the Securities Exchange Act of 1934, as amended. It is important to note that the Company’s actual results could differ materially from those projected in such forward-looking statements. Factors that could affect those results include those mentioned in the documents that the Company has filed with the Securities and Exchange Commission. In addition, we do not intend to update these statements unless it is required by the securities laws to do so, and we undertake no obligation to publicly release the result of any revisions to any such forward-looking statements that may be made to reflect events or circumstances after the date of this report or to reflect the occurrence of unanticipated events.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

99.1 Slides from presentation to be used on September 16, 2009.

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.

|  | NuStar Energy L.P.
|  | By: |  | Riverwalk Logistics, L.P.
|  |  |  | its general partner
|  | By: |  | NuStar GP, LLC
|  |  |  | its general partner
Date: September 15, 2009 |  | By: |  | /s/ Bradley C. Barron
|  |  |  | Bradley C. Barron
|  |  |  | Senior Vice President and General Counsel

EXHIBIT INDEX

Number |  | Exhibit
99.1 |  | Slides from presentation to be used on September 16, 2009.