NISOURCE INC.

Regulatory Filings • Oct 29, 2025

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): October 29, 2025

NiSource Inc.

(Exact name of registrant as specified in its charter)

DE	001-16189	35-2108964
(State or other jurisdiction of incorporation or organization)	Commission file number	(I.R.S. Employer Identification No.)

801 East 86th Avenue — Merrillville,	46410
(Address of principal executive offices)	(Zip Code)

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.

☐ 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))

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class	Trading Symbol(s)	Name of Each Exchange on Which Registered
Common Stock, par value $0.01 per share	NI	NYSE

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

ITEM 2.02. RESULTS OF OPERATIONS AND FINANCIAL CONDITION

On October 29, 2025, NiSource Inc. (the “Company”) reported its financial results for the period ended September 30, 2025. The Company’s press release, dated October 29, 2025, is attached as Exhibit 99.1.

ITEM 9.01. FINANCIAL STATEMENTS AND EXHIBITS

(d) Exhibits

Exhibit Number	Description
99.1	Press Release, dated October 29, 2025, issued by NiSource Inc.
101.INS	Inline XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document.
101.SCH	Inline XBRL Schema Document
101.CAL	Inline XBRL Calculation Linkbase Document
101.LAB	Inline XBRL Labels Linkbase Document
101.PRE	Inline XBRL Presentation Linkbase Document
101.DEF	Inline XBRL Definition Linkbase Document
104	Cover page Interactive Data File (formatted as inline XBRL, and contained in Exhibit 101.)

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.

		NiSource Inc.
		(Registrant)
Date: October 29, 2025	By:	/s/ Gunnar J. Gode
		Gunnar J. Gode
		Senior Vice President, Chief Accounting and Tax Officer (Principal Accounting Officer)