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): January 31, 2012

(Exact name of registrant as specified in its charter)

(Address of principal executive offices, including zip code)

Registrant’s telephone number, including area code: (830) 626-5200

(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. below):

Item 1.01 Entry into Material Definitive Agreement.

On January 31, 2012, Rush Enterprises, Inc. (“Rush”) and substantially all of its subsidiaries (Rush and such subsidiaries collectively, the “Company”) entered into an amended and restated Credit Agreement (the “Credit Agreement”) with General Electric Capital Corporation, as administrative agent and collateral agent (the “Agent”) for the lenders named therein, and the lenders named therein (the “Lenders”).

Pursuant to the Credit Agreement, the Lenders have agreed to make up to $600 million of revolving credit loans to finance the Company’s purchase of new and used vehicle inventory for sale by the Company and to finance the Company’s working capital needs. The revolving credit loans consist of $500 million of Revolving A Loans and $100 million of Revolving B Loans; provided that Revolving B Loans cannot be made unless there is no more availability for Revolving A Loans. Loans to purchase used inventory are limited to $125 million. Each request by the Company for a borrowing must be approved by the Agent in its sole discretion. The Company is obligated to use the proceeds from the sale of inventory to repay any loan made by the Lenders to finance such inventory; provided, however, that if the Company sells vehicles and finances the purchase of such inventory by its customer, the Company may, with the consent of the Agent, delay payment of the loan associated with such inventory until the earliest of (i) demand for payment by the Agent, (ii) receipt of payment from the customer, (iii) the date payment is due from the customer or (iv) 60 days after the vehicle was sold (which 60 day period may be extended with the consent of Lenders holding 75% in interest of the commitments); provided that the aggregate amount of outstanding loans on which payment has been delayed cannot exceed $60 million (which amount can be increased with the consent of Lenders holding 75% in interest of the commitments). In addition, with respect to each new vehicle inventory loan that remains outstanding more than 12 months, the Company must repay:

With respect to each used vehicle inventory loan that remains outstanding more than 12 months, the Company must repay:

The Company may voluntarily prepay (i) inventory loans at any time, provided that (A) prepayments cannot exceed the sum of 38% of the inventory loans made as Revolving A Loans and swing loans plus 100% of the inventory loans made as Revolving B Loans, and (B) no Revolving A Loans and swing loans may be prepaid in whole or in part if any Revolving B Loans are outstanding, and (ii) working capital loans at any time.

Borrowings under the Credit Agreement as Revolving A Loans bear interest per annum, payable monthly, at the three month LIBOR rate, determined on the last day of the prior month, plus 2.23% and borrowings under the Credit Agreement as Revolving B Loans bear interest per annum, payable monthly, at the three month LIBOR rate, determined on the last day of the prior month, plus 2.95%. In addition, the Company must pay to the Lenders a monthly working capital fee equal to 0.35% per annum multiplied by the amount of voluntary prepayments of new and used inventory loans. The Credit Agreement provides for a delinquency charge on late payments of 1.5% per month or, at the option of the Agent, 5% of the past due amount.

We have granted the Agent, for the benefit of the Lenders, a security interest in all of our present and future inventory, together with all attachments, accessories, exchanges, replacement parts, repairs, and additions to any such inventory, and all chattel paper, documents, certificates of title, certificates of origin, general intangibles, instruments, accounts and contract rights now existing or hereafter arising with respect thereto, and all cash and non-cash proceeds of any of the foregoing, in order to secure our obligations under the Credit Agreement.

The Credit Agreement expires January 31, 2015, although the Agent has the right to terminate the Credit Agreement at any time upon 120 days written notice. We may terminate the Credit Agreement at any time, although if we do so we must pay the Lenders a prepayment processing fee of $12 million if we terminate prior October 31, 2013 and $300,000 if we terminate thereafter, subject to specified limited exceptions.

The Credit Agreement requires us to meet the following financial covenants as of the last day of each quarter:

In addition to the financial covenants, the Credit Agreement limits our ability to, among other things, (i) grant liens on our assets to third parties, subject to certain customary exceptions, (ii) consolidate with, sell substantially all our assets to, or merge with a third party, (iii) change the nature of our business or (iv) enter into transactions with affiliates.

If an event of default exists under the Credit Agreement, the Lenders will be able to terminate the revolving credit facility and accelerate the maturity of all outstanding loans, as well as exercise other rights and remedies. Each of the following is an event of default under the Credit Agreement:

For purposes of this definition, Permitted Investors shall mean W. Marvin Rush, W.M. “Rusty” Rush, Robin Rush, Barbara Rush and any other person whose stock is controlled by any one or more of the foregoing.

Rush has guaranteed the borrowers’ obligations under the Credit Agreement pursuant to a Guaranty Agreement, dated as of December 31, 2010, in favor of the Agent (the “Guaranty Agreement”).

The Credit Agreement amends and restates the Company’s $450 million credit agreement, dated as of December 31, 2010, as amended, with Agent and certain of the Lenders.

The foregoing description is qualified in its entirety by reference to the full text of (i) the Credit Agreement, which is attached as Exhibit 10.1 to this Current Report on Form 8-K and incorporated in this Item 1.01 by reference, and (ii) the Guaranty Agreement, which is incorporated herein by reference to Exhibit 10.2 of Rush’s Current Report on Form 8-K (File No. 000-20797) filed January 6, 2011.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

The information described in Item 1.01 above relating to the Credit Agreement is incorporated into this Item 2.03 by reference. As of February 1, 2012, the Company had outstanding borrowings of $398,303,405 of Revolving A Loans and no outstanding borrowings under the Revolving B Loans.

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.

EXHIBIT INDEX