UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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)

April 24, 2012

Associated Banc-Corp

(Exact name of registrant as specified in its chapter)

Registrant’s telephone number, including area code 920-491-7000

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 3.03. Material Modification to Rights of Security Holders.

Item 5.03. Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

At the Annual Meeting of Shareholders of Associated Banc-Corp (the “Company”) held on April 24, 2012 (the “Annual Meeting”), shareholders of the Company approved an amendment to the Company’s Amended and Restated Articles of Incorporation relating to its preferred stock (the “Amendment”). The Amendment became effective upon filing with the Wisconsin Department of Financial Institutions on April 25, 2012. The Amendment amends and restates Article III, Section 2 of the Company’s Amended and Restated Articles of Incorporation. In addition, the Amendment deletes Article III, Sections 3, 4, 5 and 6 in their entirety, and Article III, Sections 7, 8 and 9 are re-numbered 3, 4 and 5, respectively. Previously, Article III, Sections 2, 3, 4, 5 and 6 required that any preferred stock issued by the Company include certain mandatory, minimum rights, including (1) a requirement that dividends be cumulative, (2) a limitation disallowing any dividends to be paid on the Company’s common stock if there are any accrued dividends on the preferred stock which have not been paid, or been declared and a sum set aside for payment, and (3) a liquidation preference. The Amendment has the effect of eliminating these minimum requirements with respect to preferred stock issued in the future.

The Amendment also applies to the terms of the Company’s outstanding 8.00% Perpetual Preferred Stock, Series B, liquidation preference $1,000 per share (the “Series B Preferred Stock”). At the time of issuance of the Series B Preferred Stock, the Company’s Amended and Restated Articles of Incorporation required dividends on the Series B Preferred Stock to be cumulative. By the terms of the Series B Preferred Stock, dividends on the Series B Preferred Stock became non-cumulative upon effectiveness of the Amendment.

A copy of the Articles of Amendment to the Company’s Amended and Restated Articles of Incorporation is attached hereto as Exhibit 3.1, 4.1 and is incorporated by reference herein.

Item 5.07. Submission of Matters to a Vote of Security Holders.

The results of the matters submitted to a shareholder vote at the Annual Meeting were as follows:

(1) Election of the below-named nominees to the Board of Directors (the “Board”) of the Company:

(2) Approval of the amendment of the Amended and Restated Articles of Incorporation of the Company regarding the rights and preferences of preferred stock.

(3) Approval of an advisory (non-binding) proposal on named executive officer compensation.

(4) Advisory vote on the frequency of advisory (non-binding) approval of named executive officer compensation.

(5) Ratification of KPMG LLP as the independent registered public accounting firm for the Company for the year ending December 31, 2012.

In light of the results of the advisory vote on the frequency of advisory (non-binding) approval of named executive officer compensation, the Board determined that the Company will hold an annual advisory (non-binding) vote on named executive officer compensation. The Board will reevaluate this determination after the next shareholder advisory vote on the frequency of advisory (non-binding) approval of named executive officer compensation.

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