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

July 21, 0000

Xxxxx Xxxxxx Bank and Trust Company

Xxx Xxxxxxxx Xxxxx

Xxxxx Xxxxxx, Xxxxxxxxxxxxx 00000

Location Code: OHD0310

Attention:  Xxxxxxx X. Xxxxxxx

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 Fund

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

American Century ETF Trust – Avantis Core Municipal Fixed Income 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 Core Fixed Income Fund

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

American Century ETF Trust – Avantis Core Municipal Fixed Income Fund.

            By:     /s/ Xxxx X. Xxxxx

            Name:     Xxxx X. Xxxxx

            Title:     Vice President, Duly Authorized

Agreed and Accepted:

STATE STREET BANK AND TRUST COMPANY

By:     /s/ Xxxxx Xxxxxx

Name:    Xxxxx Xxxxxx

Title:    Senior Vice President

Effective Date: July 21, 2020