The men's 400 metres event at the 2019 European Athletics U23 Championships was held in Gävle, Sweden, at Gavlehof Stadium Park on 11, 12, and 13 July.
[1] Prior to the competition, the records were as follows: Qualification rule: First 3 (Q) and the next 4 fastest (q) qualified for the semifinals.
Qualification: First 3 in each heat (Q) and next 2 fastest (q) qualified for the final.