August 13, 2019 State Street Bank and Trust Company Josiah Quincy Building

August 13, 0000

Xxxxx Xxxxxx Bank and Trust Company

Xxxxxx Xxxxxx Building

000 Xxxxxxx Xxxxxx

Xxxxx Xxxxxx, Xxxxxxxxxxxxx 00000

Location Code: JQB5

Attention: Xxxxxxx X Xxxxxxx

Re: Transfer Agency and Service 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 ETF

American Century ETF Trust - Avantis International Equity ETF

American Century ETF Trust - Avantis Emerging Markets Equity ETF

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

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

In accordance with Section 12, the Additional Trusts and Portfolios provision, of the Transfer Agency and Service Agreement dated as of January 9, 2018, (the “Transfer Agent Agreement”) by and among each Trust party thereto and State Street Bank and Trust Company, the undersigned Trust hereby requests that your bank act as Transfer Agent for the respective New Portfolios under the terms of the Transfer Agent Agreement. In connection with such request, the undersigned Trust hereby confirms to you, as of the date hereof, its representations and warranties set forth in Section 4 of the Transfer Agent Agreement. Capitalized terms used herein without definition shall have the meanings ascribed to them in the Transfer Agent Agreement.

Kindly indicate your acceptance of the foregoing by executing two copies of this letter agreement, returning one to the Trust and retaining one for your records.

Sincerely,

American Century Investment Management, Inc. on behalf of American Century ETF Trust - Avantis U.S. Equity ETF

American Century ETF Trust - Avantis International Equity ETF

American Century ETF Trust - Avantis Emerging Markets Equity ETF

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

American Century ETF Trust - Avantis International Small Cap Value ETF

By: /s/ C. Xxxx Xxxx

Name: C. Xxxx Xxxx

Title: Vice President, Duly Authorized

Agreed and Accepted:

STATE STREET BANK AND TRUST COMPANY

By: /s/ Xxxxxx Xxxxxxxx

Name: Xxxxxx Xxxxxxxx

Title: Executive Vice President

Effective Date: August 27, 2019