The men's 400 metres competition of the athletics events at the 2023 Pan American Games was held on October 30 and November 1 at the Julio Martínez National Stadium of Santiago, Chile.

[1] Prior to this competition, the existing world and Pan American Games records were as follows: All times shown are in seconds.

Qualification: First 2 in each heat (Q) and next 2 fastest (q) qualified for the final.

The results were as follows:[2] The results were as follows:[3]