July 21, 2020

State Street Bank and Trust Company

One Heritage Drive

North Quincy, Massachusetts 02171

Location Code: OHD0310

Attention: Russell M Donohoe

Re: Master Custodian Agreement - New Portfolios

Ladies and Gentlemen:

Please be advised that the undersigned Fund has established three (3) new series of shares to be known as:

American Century ETF Trust - Avantis Core Fixed Income ETF

American Century ETF Trust - Avantis Short-Term Fixed Income ETF

American Century ETF Trust - Avantis Core Municipal Fixed Income ETF (the “New ETF 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 New ETF Portfolios under the terms of the Custodian Agreement. In connection with such request, the 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. 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 two copies of this letter agreement, returning one to the Fund and retaining one for your records.

Sincerely,

American Century Investment Management, Inc. on behalf of

American Century ETF Trust - Avantis Core Fixed Income ETF

American Century ETF Trust - Avantis Short-Term Fixed Income ETF

American Century ETF Trust - Avantis Core Municipal Fixed Income ETF

By: /s/ Otis H. Cowan

Otis H. Cowan

Title: Vice President, Duly Authorized

Agreed and Accepted:

STATE STREET BANK AND TRUST COMPANY

By:     /s/ Jason Becker

Name:Jason Becker

Title:Senior Vice President

Effective Date: July 21, 2020