CABOT CORP

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

For the fiscal year ended September 30,2025

or

For the transition period from to

Commission File Number 1-5667

Cabot Corporation

(Exact name of Registrant as specified in its Charter)

Registrant’s telephone number, including area code: (617)345-0100

Securities registered pursuant to Section 12(b) of the Securities Exchange Act of 1934:

Securities registered pursuant to Section 12(g) of the Securities Exchange Act of 1934: None.

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.

Yes ☒ No☐

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.

Yes☐ No ☒

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No☐

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See definitions of “large accelerated filer,” “accelerated filer”, “smaller reporting company”, and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by checkmark 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.☐

Indicate by check mark whether the Registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive‐based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D‐1(b). ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

Yes☐ No☒

As of the last business day of the Registrant’s most recently completed second fiscal quarter (March 31, 2025), the aggregate market value of the Registrant’s common stock held by non-affiliates was $4,429,047,299. As of November 14, 2025, there were 52,898,776 shares of the Registrant’s common stock outstanding.

Portions of the Registrant’s definitive proxy statement for its 2026 Annual Meeting of Shareholders are incorporated by reference into Part III of this report.

TABLE OF CONTENTS

Information Relating to Forward-Looking Statements

This annual report on Form 10-K contains “forward-looking statements” under the Federal securities laws. These forward-looking statements address expectations or projections about the future, including our expectations regarding our future business performance and overall prospects, including for earnings before interest and taxes (“EBIT”) in our business segments, and the principal assumptions underlying these expectations, including the possible impact of our relationship with Dow on our operations in Barry, Wales, and demand for our products; the sufficiency of our cash on hand, cash provided from operations and cash available under our credit and commercial paper facilities to fund our cash requirements in both the next twelve months and the foreseeable future; anticipated capital spending; regulatory developments, including regulatory compliance costs and potential impact on our operations; cash requirements and uses of available cash, including future cash outlays associated with respirator liabilities and the timing of such outlays; amortization expenses; our operating tax rate; timing of the expected closing of our acquisition in Mexico and when we expect to restart operations at our aerogel manufacturing plant; our plan to refinance our $250 million in notes with a coupon of 3.4% that mature in September 2026 prior to their maturity; and the possible outcome of legal and environmental proceedings. From time to time, we also provide forward-looking statements in other materials we release to the public and in oral statements made by authorized officers.

Forward-looking statements are not guarantees of future performance and are subject to risks, uncertainties, potentially inaccurate assumptions, and other factors, some of which are beyond our control or difficult to predict. If known or unknown risks materialize, our actual results could differ materially from past results and from those expressed in the forward-looking statements. Important factors that could cause our actual results to differ materially from those expressed in our forward-looking statements are described in Item 1A in this report.

We undertake no obligation to publicly update forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. Investors are advised, however, to consult any further disclosures we make on related subjects in our 10-Q and 8-K reports filed with the Securities and Exchange Commission (the “SEC”).