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): May 14, 2013

NiSource Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code (877) 647-5990

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.

Item 5.07 Submission of Matters to a Vote of Security Holders

On May 14, 2013, the Company held its Annual Meeting of Stockholders (the “Annual Meeting”). Set forth below are the matters acted upon by Company stockholders at the Annual Meeting as described in the Company’s Proxy Statement filed on April 12, 2013, and the final voting results on each such matter.

Proposal I: Election of Directors. The number of votes cast for and against each nominee, as well as the number of abstentions and broker non-votes, were as follows:

Each nominee, having received more votes in favor of his or her election than against election, was elected.

Proposal II: Ratification of Independent Registered Public Accountants. The number of votes cast for and against this matter, as well as the number of abstentions, were as follows:

There were no broker non-votes as to Proposal II.

Proposal II, having received the affirmative vote of the holders of at least a majority of the shares of common stock present or represented by proxy and entitled to vote at the Annual Meeting, was approved.

Proposal III: Advisory Approval of Executive Compensation. The number of votes cast for and against this matter, as well as the number of abstentions, were as follows:

There were 23,396,465 broker non-votes as to Proposal III.

Proposal III, having received the affirmative vote of the holders of at least a majority of the shares of common stock present or represented by proxy and entitled to vote at the Annual Meeting, was approved on an advisory basis.

Proposal IV: Stockholder Proposal Regarding Action by Written Consent. The number of votes cast for and against this matter, as well as the number of abstentions, were as follows:

There were 23,396,465 broker non-votes as to Proposal IV.

Proposal IV, having failed to receive the affirmative vote of the holders of at least a majority of the shares of common stock present or represented by proxy and entitled to vote at the Annual Meeting, was not approved.

Proposal V: Stockholder Proposal to Establish a Policy to End Benchmarking CEO Compensation. The number of votes cast for and against this matter, as well as the number of abstentions, were as follows:

There were 23,396,465 broker non-votes as to Proposal V.

Proposal V, having failed to receive the affirmative vote of the holders of at least a majority of the shares of common stock present or represented by proxy and entitled to vote at the Annual Meeting, was not approved.

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.