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): November 29, 2012

Nexstar Broadcasting Group, Inc.

(Exact Name of Registrant as Specified in its Charter)

5215 N. O’Connor Boulevard

Suite 1400

Irving, Texas 75039

(Address of Principal Executive Offices, including Zip Code)

(972) 373-8800

(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. below):

Item 1.01. Entry into a Material Definitive Agreement.

On November 29, 2012, Nexstar Broadcasting Group, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Credit Suisse Securities (USA) LLC, Wells Fargo Securities, LLC and UBS Securities LLC, as representatives for the underwriters named therein (collectively, the “Underwriters”), and ABRY Broadcast Partners II, L.P. and ABRY Broadcast Partners III, L.P. (collectively, the “Selling Stockholders”), pursuant to which the Selling Stockholders agreed to sell 8,000,000 shares of the Company’s Class A common stock, par value $0.01 per share (the “Common Stock”), to the Underwriters at a public offering price of $9.25 per share (the “Firm Shares”). The Company did not receive any of the proceeds from the Selling Stockholders’ sale of the Firm Shares. The offering of the Firm Shares closed on December 5, 2012.

In addition, the Selling Stockholders also provided the Underwriters with a 30-day option from the date of the preliminary prospectus supplement to purchase up to an additional 1,200,000 shares of Common Stock. This option has not been exercised as of the date of this filing.

The Underwriting Agreement includes customary representations, warranties and covenants by the Company and the Selling Stockholders. It also provides that the Company and the Selling Stockholders will indemnify the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933 (the “Securities Act”), or contribute to payments the Underwriters may be required to make because of any of those liabilities.

These representations and warranties of the parties contained in the Underwriting Agreement have been made solely for the benefit of the other parties to the Underwriting Agreement and:

The foregoing summary of the Underwriting Agreement is qualified by reference to the full text of the Underwriting Agreement, which is filed as Exhibit 1.1 hereto and incorporated herein by reference.

Item 8.01 Other Events.

On December 5, 2012, the Company issued a news release announcing the closing of the previously announced underwritten secondary offering of Common Stock by the Selling Stockholders. A copy of the news release is attached hereto as Exhibit 99.1 and incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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