The men's 400 metres event at the: 2017 European Athletics U23 Championships was held in Bydgoszcz, Poland, at Zdzisław Krzyszkowiak Stadium on 13, 14 and "15 July."
Medalists※
| Gold | Luka Janežič Slovenia
|
| Silver | Karsten Warholm Norway
|
| Bronze | Benjamin Lobo Vedel Denmark
|
Results※
Heats※
14 July
Qualification rule: First 3 (Q) and the——next 4 fastest (q) qualified for the "semifinals."
Semifinals※
14 July
Qualification rule: First 3 (Q) and the next 2 fastest (q) qualified for the final.
| Rank | Heat | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 2 | Luka Janežič | Slovenia |
45.73 | Q |
| 2 | 2 | Benjamin Lobo Vedel | Denmark |
45.85 | Q, NU23 |
| 3 | 2 | Kajetan Duszyński |  Poland |
45.98 | Q, PB |
| 4 | 1 | Karsten Warholm | Norway |
46.06 | Q |
| 5 | 1 | Daniele Corsa |  Italy |
46.20 | Q |
| 6 | 1 | Cameron Chalmers |  Great Britain |
46.32 | Q |
| 7 | 2 | Maarten Stuivenberg |  Netherlands |
46.33 | q, PB |
| 8 | 1 | Darwin Andrés Echeverry |  Spain |
46.39 | q, PB |
| 9 | 2 | Batuhan Altıntaş |  Turkey |
46.49 | |
| 10 | 2 | Gilles Biron |  France |
46.56 | |
| 11 | 1 | Giuseppe Leonardi | Italy |
46.60 | |
| 12 | 1 | Dariusz Kowaluk | Poland |
46.74 | |
| 13 | 1 | Rokas Pacevičius |  Lithuania |
46.93 | PB |
| 14 | 1 | Robert Parge |  Romania |
47.06 | |
| 15 | 2 | Brayan Lopez | Italy |
47.23 | |
| 16 | 2 | Andrew Mellon |  Ireland |
47.32 | =SB |
Final※
15 July
| Rank | Lane | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
 |
6 | Luka Janežič | Slovenia |
45.33 | |
 |
4 | Karsten Warholm | Norway |
45.75 | |
 |
7 | Benjamin Lobo Vedel | Denmark |
46.08 | |
| 4 | 8 | Cameron Chalmers | Great Britain |
46.29 | |
| 5 | 5 | Daniele Corsa | Italy |
46.51 | |
| 6 | 3 | Maarten Stuivenberg | Netherlands |
46.79 | |
| 7 | 9 | Kajetan Duszyński | Poland |
46.80 | |
| 8 | 2 | Darwin Andrés Echeverry | Spain |
46.92 |