September 6, 2019

State Street Bank and Trust Company

Josiah Quincy Building

200 Newport Avenue

North Quincy, Massachusetts 02171

Location Code: JQB5

Attention: Russell M Donohoe

Re: Master Custodian Agreement - New Portfolios

Ladies and Gentlemen:

Please be advised that the undersigned Fund has established five (5) new series of shares to be known as American Century ETF Trust - Avantis U.S. Equity Fund

American Century ETF Trust - Avantis International Equity Fund

American Century ETF Trust - Avantis Emerging Markets Equity Fund

American Century ETF Trust - Avantis U.S. Small Cap Value Fund

American Century ETF Trust - Avantis International Small Cap Value Fund (the “New Portfolios”).

In accordance with Section 18.6, the Additional Portfolios provision, of the Master Custodian Agreement dated as of July 29, 2011, (the “Custodian Agreement”) by and among each Fund party thereto and State Street Bank and Trust Company, the undersigned Fund hereby requests that your bank act as Custodian for the respective New Portfolios under the terms of the Custodian Agreement. In connection with such request, each undersigned Fund hereby confirms to you, as of the date hereof, its representations and warranties set forth in Section 18.7 of the Custodian Agreement. For the avoidance of doubt, the New Portfolios shall not be treated as ETF Portfolios under the Custodian Agreement as amended pursuant to the letter amendment dated January 9, 2018 (“ETF Letter Amendment”) with regard to Sections 2.14, 2.15, 6 and 10.1 as amended or added thereby. Capitalized terms used herein without definition shall have the meanings ascribed to them in the Custodian Agreement.

Kindly indicate your acceptance of the foregoing by executing this letter agreement and returning a copy to the Fund.

Sincerely,

American Century Investment Management, Inc. on behalf of

American Century ETF Trust - Avantis U.S. Equity Fund

American Century ETF Trust - Avantis International Equity Fund

American Century ETF Trust - Avantis Emerging Markets Equity Fund

American Century ETF Trust - Avantis U.S. Small Cap Value Fund

American Century ETF Trust - Avantis International Small Cap Value Fund

By: /s/ Otis H. Cowan

Name: Otis H. Cowan

Title: Vice President, Duly Authorized

Agreed and Accepted:

STATE STREET BANK AND TRUST COMPANY

By: /s/ Andrew Erickson

Name:Andrew Erickson

Title:Executive Vice President

Effective Date: December 3, 2019