Jul. 02, 2018

American Century ETF Trust | American Century Diversified Corporate Bond ETF

American Century ETF Trust

Summary Prospectus and Prospectus Supplement

American Century Diversified Corporate Bond ETF

Supplement dated July 2, 2018 nSummary Prospectus and Prospectus dated January 9, 2018

The following is added under the Principal Risks section on pages 2 and 3 of the summary prospectus and prospectus and under the What are the principal risks of investing in the fund? subsection on pages 5-7 of the prospectus:

Certain shareholders, including other funds advised by the adviser, may from time to time own a substantial amount of the shares of the fund. In addition, a third party investor, the adviser or an affiliate of the adviser, an authorized participant, a market maker, or another entity may invest in the fund and hold its investment for a limited period of time solely to facilitate commencement of the fund or to facilitate the fund’s achieving a specified size or scale. There can be no assurance that any large shareholder would not redeem its investment, that the size of the fund would be maintained at such levels or that the fund would continue to meet applicable listing requirements. Redemptions by large shareholders could have a significant negative impact on the fund. In addition, transactions by large shareholders may account for a large percentage of the trading volume on the NYSE Arca, Inc. and may, therefore, have a material upward or downward effect on the market price of the shares.