SCHEDULE 13G/A 0001827977 XXXXXXXX LIVE 6 Common Stock, par value $0.01 per share 03/06/2026 0001822479 Sotera Health Co. 83601L102 9100 South Hills Blvd Suite 300 Broadview Heights OH 44147 Rule 13d-1(d) GTCR INVESTMENT XI LLC b DE 0.00 31838253.00 0.00 12735301.00 31838253.00 N 11.2 OO (1) As more fully described in Item 4 of this Amendment No. 6 to Schedule 13G, the GTCR Investors (as defined in Item 2) are party to a Stockholders Agreement with the Warburg Pincus Investors (as defined in Item 4) and certain other holders of Common Stock of the Issuer. The GTCR Investors, together with the Warburg Pincus Investors, hold an aggregate total of 31,838,253 shares of Common Stock of the Issuer (approximately 11.2% of the outstanding shares of Common Stock of the Issuer), of which 19,102,952 shares of Common Stock are publicly reported as being owned by the Warburg Pincus Investors in such entities' Form 4, filed with the U.S. Securities and Exchange Commission ("Commission") on March 10, 2026. Although the GTCR Reporting Persons (as defined in Item 2) may be deemed to beneficially own the Common Stock held of record by the Warburg Pincus Investors as a result of the Stockholders Agreement, each GTCR Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Securities Exchange Act of 1934, as amended (the "Exchange Act")) with respect to any shares of Common Stock other than the shares of Common Stock of the Issuer owned of record by such GTCR Reporting Person. The percentages used herein have been determined in accordance with footnote 2 below. Capitalized terms used herein are defined in Items 2(a) or 4 below. (2) Calculated based on 284,392,079 shares of Common Stock outstanding as of February 17, 2026 as reported on the Issuer's final prospectus supplement, filed pursuant to Rule 424(b)(7) on March 5, 2026. GTCR FUND XI/A LP b DE 0.00 31838253.00 0.00 10107727.00 31838253.00 N 11.2 PN (1) As more fully described in Item 4 of this Amendment No. 6 to Schedule 13G, the GTCR Investors are party to a Stockholders Agreement with the Warburg Pincus Investors and certain other holders of Common Stock of the Issuer. The GTCR Investors, together with the Warburg Pincus Investors, hold an aggregate total of 31,838,253 shares of Common Stock of the Issuer (approximately 11.2% of the outstanding shares of Common Stock of the Issuer), of which 19,102,952 shares of Common Stock are publicly reported as being owned by the Warburg Pincus Investors in such entities' Form 4, filed with the Commission on March 10, 2026. Although the GTCR Reporting Persons may be deemed to beneficially own the Common Stock held of record by the Warburg Pincus Investors as a result of the Stockholders Agreement, each GTCR Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock other than the shares of Common Stock of the Issuer owned of record by such GTCR Reporting Person. The percentages used herein have been determined in accordance with footnote 2 below. Capitalized terms used herein are defined in Items 2(a) or 4 below. (2) Calculated based on 284,392,079 shares of Common Stock outstanding as of February 17, 2026 as reported on the Issuer's final prospectus supplement, filed pursuant to Rule 424(b)(7) on March 5, 2026. GTCR FUND XI/C LP b DE 0.00 31838253.00 0.00 2546564.00 31838253.00 N 11.2 PN (1) As more fully described in Item 4 of this Amendment No. 6 to Schedule 13G, the GTCR Investors are party to a Stockholders Agreement with the Warburg Pincus Investors and certain other holders of Common Stock of the Issuer. The GTCR Investors, together with the Warburg Pincus Investors, hold an aggregate total of 31,838,253 shares of Common Stock of the Issuer (approximately 11.2% of the outstanding shares of Common Stock of the Issuer), of which 19,102,952 shares of Common Stock are publicly reported as being owned by the Warburg Pincus Investors in such entities' Form 4, filed with the Commission on March 10, 2026. Although the GTCR Reporting Persons may be deemed to beneficially own the Common Stock held of record by the Warburg Pincus Investors as a result of the Stockholders Agreement, each GTCR Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock other than the shares of Common Stock of the Issuer owned of record by such GTCR Reporting Person. The percentages used herein have been determined in accordance with footnote 2 below. Capitalized terms used herein are defined in Items 2(a) or 4 below. (2) Calculated based on 284,392,079 shares of Common Stock outstanding as of February 17, 2026 as reported on the Issuer's final prospectus supplement, filed pursuant to Rule 424(b)(7) on March 5, 2026. GTCR CO-INVEST XI LP b DE 0.00 31838253.00 0.00 81010.00 31838253.00 N 11.2 PN (1) As more fully described in Item 4 of this Amendment No. 6 to Schedule 13G, the GTCR Investors are party to a Stockholders Agreement with the Warburg Pincus Investors and certain other holders of Common Stock of the Issuer. The GTCR Investors, together with the Warburg Pincus Investors, hold an aggregate total of 31,838,253 shares of Common Stock of the Issuer (approximately 11.2% of the outstanding shares of Common Stock of the Issuer), of which 19,102,952 shares of Common Stock are publicly reported as being owned by the Warburg Pincus Investors in such entities' Form 4, filed with the Commission on March 10, 2026. Although the GTCR Reporting Persons may be deemed to beneficially own the Common Stock held of record by the Warburg Pincus Investors as a result of the Stockholders Agreement, each GTCR Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock other than the shares of Common Stock of the Issuer owned of record by such GTCR Reporting Person. The percentages used herein have been determined in accordance with footnote 2 below. Capitalized terms used herein are defined in Items 2(a) or 4 below. (2) Calculated based on 284,392,079 shares of Common Stock outstanding as of February 17, 2026 as reported on the Issuer's final prospectus supplement, filed pursuant to Rule 424(b)(7) on March 5, 2026. GTCR PARTNERS XI/A&C LP b DE 0.00 31838253.00 0.00 12654291.00 31838253 N 11.2 PN (1) As more fully described in Item 4 of this Amendment No. 6 to Schedule 13G, the GTCR Investors are party to a Stockholders Agreement with the Warburg Pincus Investors and certain other holders of Common Stock of the Issuer. The GTCR Investors, together with the Warburg Pincus Investors, hold an aggregate total of 31,838,253 shares of Common Stock of the Issuer (approximately 11.2% of the outstanding shares of Common Stock of the Issuer), of which 19,102,952 shares of Common Stock are publicly reported as being owned by the Warburg Pincus Investors in such entities' Form 4, filed with the Commission on March 10, 2026. Although the GTCR Reporting Persons may be deemed to beneficially own the Common Stock held of record by the Warburg Pincus Investors as a result of the Stockholders Agreement, each GTCR Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock other than the shares of Common Stock of the Issuer owned of record by such GTCR Reporting Person. The percentages used herein have been determined in accordance with footnote 2 below. Capitalized terms used herein are defined in Items 2(a) or 4 below. (2) Calculated based on 284,392,079 shares of Common Stock outstanding as of February 17, 2026 as reported on the Issuer's final prospectus supplement, filed pursuant to Rule 424(b)(7) on March 5, 2026. Sotera Health Co. The Company's principal executive offices are located at 9100 South Hills Blvd, Suite 300, Broadview Heights, OH, 44147. This Amendment No. 6 to Schedule 13G is being filed jointly by (i) GTCR Investment XI LLC, a Delaware limited liability company ("Investment XI"), (ii) GTCR Fund XI/A LP, a Delaware limited partnership ("Fund XI/A"), (iii) GTCR Fund XI/C LP, a Delaware limited partnership ("Fund XI/C"), (iv) GTCR Co-Invest XI LP, a Delaware limited partnership ("Co-Invest XI", and together, with Fund XI/A and Fund XI/C, the "GTCR XI Funds or GTCR Investors"), and (v) GTCR Partners XI/A&C LP, a Delaware limited partnership ("Partners XI/A&C"), and which is the general partner of each of Fund XI/A and Fund XI/C. Investment XI is the general partner of Co-Invest XI and Partners XI/A&C. Investment XI is managed by a board of managers (the "GTCR Board of Managers") consisting of Mark M. Anderson, Aaron D. Cohen, Sean L. Cunningham, David A. Donnini, Constantine S. Mihas and Collin E. Roche, and no single person has voting or dispositive authority over the shares of Common Stock. The GTCR XI Funds, Partners XI/A&C and Investment XI are collectively referred to herein as the "GTCR Reporting Persons". The principal business address of each of the GTCR Reporting Persons is 300 North LaSalle Street, Suite 5600, Chicago, IL 60654. Y The information required by Items 4(a)-(c) is set forth in Rows 5-11 of the cover page hereto for each GTCR Reporting Person and is incorporated herein by reference for each such GTCR Reporting Person. On November 19, 2020, (i) the Issuer, (ii) Warburg Pincus Private Equity XI, L.P., Warburg Pincus Private Equity XI-B, L.P., Warburg Pincus Private Equity XI-C, L.P., WP XI Partners, L.P. and Bull Co-Invest, L.P. (collectively, the "Warburg Pincus Sponsors" or "Warburg Pincus Investors"), (iii) the GTCR XI Funds and (iv) certain other holders of Common Stock of the issuer ( the "Other Investors"), entered into a Stockholders Agreement (the "Stockholders Agreement"). The Stockholders Agreement sets forth certain governance arrangements with respect to the Issuer, transfer restrictions on Other Investors and indemnification matters. Pursuant to the Stockholders Agreement, each of the Warburg Pincus Sponsors and the GTCR XI Funds has agreed to vote the shares of Common Stock of the Issuer that each holds of record in a certain manner on matters related to the election of certain directors appointed by the Warburg Pincus Sponsors and the GTCR XI Funds. The Warburg Pincus Sponsors and the GTCR XI Funds hold an aggregate total of 31,838,253 shares of Common Stock of the Issuer (approximately 11.2% of the outstanding shares of Common Stock of the Issuer), including 12,735,301 shares of Common Stock owned by the GTCR XI Funds and 19,102,952 shares of Common Stock owned by the Warburg Pincus Sponsors. The GTCR Reporting Persons are not entitled to any rights as a stockholder of the Issuer with respect to the shares of Common Stock of the Issuer beneficially owned by the Other Investors or the Warburg Pincus Sponsors except as expressly set forth in the Stockholders Agreement and the GTCR Reporting Persons do not have dispositive power over the Common Stock owned by the Warburg Pincus Sponsors. Each GTCR Reporting Person and each of the individual members of the GTCR Board of Managers expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock of the Issuer other than the shares of Common Stock of the Issuer owned of record by a GTCR Reporting Person. The number of shares of Common Stock of the Issuer owned by each GTCR Reporting Person as set forth in Rows 5 - 11 of their respective cover pages to this Schedule 13G does not reflect the aggregate shares of Common Stock of the Issuer owned by the Other Investors. The aggregate total of 19,102,952 shares of Common Stock of the Issuer indicated in this Amendment No. 6 to Schedule 13G as being beneficially owned by the Warburg Pincus Sponsors is derived from the Warburg Pincus Sponsors' Form 4, filed with the Commission on March 10, 2026, and is not purported to be an accurate representation of the Warburg Pincus Sponsors' beneficial ownership as of the date of this Amendment No. 6 to Schedule 13G. The Warburg Pincus Sponsors are responsible for reporting their beneficial ownership of shares of Common Stock of the Issuer on their own behalf, and the GTCR Reporting Persons disclaim responsibility for reporting the shares of Common Stock of the Issuer beneficially owned by the Warburg Pincus Sponsors. The percentages used herein are calculated based on 284,392,079 shares of Common Stock outstanding as of February 17, 2026 as reported on the Issuer's final prospectus supplement, filed pursuant to Rule 424(b)(7) on March 5, 2026. Y N Y N (1) The GTCR Reporting Persons are making this single, joint filing because they may be deemed to constitute a "group" within the meaning of the Exchange Act. The joint filing agreement among the GTCR Reporting Persons to file this Amendment No. 6 to Schedule 13G jointly in accordance with Rule 13d-1(k) of the Exchange Act is incorporated by reference as Exhibit 99.1. (2) Each GTCR Reporting Person expressly disclaims beneficial ownership (within the meaning of Rule 13d-3 of the Exchange Act) with respect to any shares of Common Stock of the issuer other than the shares of Common Stock of the issuer owned of record by such GTCR Reporting Person. Y Y GTCR INVESTMENT XI LLC /s/ Jeffrey Wright 03/10/2026 GTCR FUND XI/A LP /s/ Jeffrey Wright 03/10/2026 GTCR FUND XI/C LP /s/ Jeffrey Wright 03/10/2026 GTCR CO-INVEST XI LP /s/ Jeffrey Wright 03/10/2026 GTCR PARTNERS XI/A&C LP /s/ Jeffrey Wright 03/10/2026 Exhibit 99.1 Agreement of Joint Filing as required by Rule 13d-1(k)(1) under the Act.* * Incorporated herein by reference to the Agreement of Joint Filing by GTCR Investment XI LLC, GTCR Fund XI/A LP, GTCR Fund XI/C LP, GTCR Co-Invest XI LP and GTCR Partners XI/A&C LP dated as of February 11, 2022, which was previously filed with the Commission as Exhibit A to Amendment No. 1 to Schedule 13G filed by GTCR Investment XI LLC, GTCR Fund XI/A LP, GTCR Fund XI/C LP, GTCR Co-Invest XI LP and GTCR Partners XI/A&C LP on February 11, 2022 with respect to the shares of common stock of Sotera Health Co.