The men's 400 metres was a track & field athletics event at the 1900 Summer Olympics in Paris.

His countryman Dixon Boardman was a strong challenger, having beaten Long at the 1900 IC4A.

(*) unofficial 440 yards (= 402.34 m) Maxie Long set a new Olympic record in the first round with 50.4 seconds.

This heat, featuring four American runners, resulted in an easy win for Long and the top three spots for the United States team.

Boardman, Lee, and Moloney all withdrew because the final was held on a Sunday, but Long and Holland elected to start.