[1] The event was won by Rex Cawley of the United States, the nation's sixth consecutive and 11th overall victory in the men's 400 metres hurdles.

It had been introduced along with the men's 200 metres hurdles in 1900, with the 200 being dropped after 1904 and the 400 being held through 1908 before being left off the 1912 programme.

However, when the Olympics returned in 1920 after World War I, the men's 400 metres hurdles was back and would continue to be contested at every Games thereafter.

American Rex Cawley was the favorite after setting a world record at the U.S. trials; he was also the 1963 AAU champion.

The United States made its 13th appearance, the only nation to have competed at every edition of the event to that point.