The men's T20 400 metres competition of the athletics events at the 2023 Parapan American Games was held on November 23 - 24 at the Mario Recordón Athletics Training Center within 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.

The fastest two athletes of each semifinal advance to the final.

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