The Men's 400 metres T20 at the 2024 Summer Paralympics took place on 3 September 2024 at the Stade de France in Paris.

[1] The T20 category is for athletes with intellectual impairment.

T20 athletes have an IQ score of 75 or less.

The T20 event was a straight final with eight entrants.

The final in this classification took place on 3 September 2024, at 20:36: