Avantor, Inc.

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. On September 21, 2026, Avantor, Inc. (the “Company”), announced the appointment of Todd Garner as Executive Vice President and Chief Financial Officer, effective as of September 21, 2026 (the “Commencement Date”). Upon the Commencement Date, Mr. Garner will become a member of the Company’s Executive Leadership Team and serve as its principal financial officer. Prior to joining the Company, Mr. Garner, age 57, served as Executive Vice President and Chief Financial Officer of CONMED Corporation, a medical technology company, from January 2018 until March 2026. Prior to that, Mr. Garner served in several roles at C.R. Bard, Inc, a specialty medical products company, from 2003 until 2017, including Vice President, Investor Relations from 2011 until 2017, Vice President, Controller (Division Chief Financial Officer) from 2007 until 2011, Director of Financial Reporting from 2005 to 2007, and Controller of the Reynosa Operations from 2003 to 2005. Mr. Garner holds a bachelor’s degree in accounting from Brigham Young University and an MBA from the University of Texas - Rio Grande Valley. Mr. Garner is also a Certified Public Accountant. In connection with the appointment of Mr. Garner as Executive Vice President and Chief Financial Officer, on September 17, 2026, the Company entered into an employment letter agreement (the “Employment Letter”) with Mr. Garner. Pursuant to the Employment Letter, Mr. Garner’s annual base salary is $700,000 and he is eligible to participate in the Company’s incentive-based annual cash program beginning in 2026, pro-rated based on his start date, with an annual target bonus opportunity of 80% of his annual base salary. Mr. Garner will also receive a one-time cash signing bonus of $150,000, subject to certain repayment obligations in the event of his departure prior to the one-year anniversary of the Commencement Date. The Employment Letter also provides for an initial long-term equity grant under the Company’s 2019 Equity Incentive Plan (the “Plan”) in the target amount of $1,500,000, half of which will be granted in the form of restricted stock units and half will be granted in the form of stock options issued at a 10% premium to the closing price of a share of the Company’s common stock on the grant date. The stock options will vest ratably over three years, and the restricted stock units will vest ratably over two years, in each case, subject to the Plan’s terms and conditions. In future years, Mr. Garner will be eligible to participate in the Company’s long-term incentive program, with a target annual grant of $3,000,000, allocated in the same manner applicable to all members of the Company’s Executive Leadership Team. Mr. Garner will also be eligible to participate in the Company’s Executive Severance and Change in Control Plan, which is described in the Company’s current report on Form 8-K, filed with the Securities and Exchange Commission on May 12, 2025, and a copy of which will be filed with the Company’s quarterly report on Form 10-Q for the quarter ending June 30, 2026. The foregoing description of the Employment Letter is a summary only and does not purport to be complete and is qualified in its entirety by reference to the full text, a copy of which is attached hereto as Exhibit 10.1 to this Current Report on Form 8-K, which is incorporated herein by reference. The Company confirms that (1) there is no arrangement or understanding between Mr. Garner and any other person pursuant to which he was appointed as Executive Vice President and Chief Financial Officer, (2) there is no family relationship between Mr. Garner and any director or executive officer of the Company, and (3) there are no transactions involving Mr. Garner that would require disclosure under Item 404(a) of Regulation S-K. Upon the Commencement Date, Steven Eck, the Company’s Senior Vice President, Interim Chief Financial Officer and Chief Accounting Officer, will cease serving as the Interim Chief Financial Officer, but will continue in his position as Senior Vice President and Chief Accounting Officer.

Item 7.01. Regulation FD Disclosure. On September 21, 2026, the Company issued a press release announcing the appointment of Mr. Garner. A copy of the press release is furnished herewith as Exhibit No. 99.1 to this Current Report on Form 8-K and incorporated herein by reference. The information in this Item 7.01, including Exhibit 99.1, is furnished and shall not be deemed filed for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section and shall not be deemed to be incorporated by reference into any filing by the Company under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.