The men's 400 metres at the 2024 World Athletics Indoor Championships took place on 1 and 2 March 2024.

Qualification: First 2 in each heat (Q) and the next 4 fastest (q) advance to the Semi-Finals The heats were started on 1 March at 11:52.

[1] Qualification: First 3 in each heat (Q) advance to the final.

The heats were started on 1 March at 21:10.

[2] The final was started on 2 March at 21:10.