The Men's 400 metres event at the 2011 European Athletics U23 Championships was held in Ostrava, Czech Republic, at Městský stadion on 14 and 16 July.
| Gold | Nigel Levine | |
| Silver | Brian Gregan | |
| Bronze | Luke Lennon-Ford |
16 July 2011 / 16:40
| Rank | Name | Nationality | Lane | Reaction Time | Time | Notes | |||
|---|---|---|---|---|---|---|---|---|---|
| align=left | align=left | 6 | 0.174 | 46.10 | |||||
| align=left | align=left | | 5 | 0.172 | 46.12 | PB | |||
| align=left | align=left | 4 | 0.190 | 46.22 | |||||
| 4 | align=left | align=left |  | 3 | 0.226 | 46.29 | SB | ||
| 5 | align=left | align=left |  | 1 | 0.224 | 46.32 | PB | ||
| 6 | align=left | align=left |  | 8 | 0.160 | 46.33 | |||
| 7 | align=left | align=left |  | 2 | 0.161 | 46.56 | PB | ||
| 8 | align=left | align=left | | 7 | 0.194 | 46.96 |
Qualified: First 2 in each heat (Q) and 2 best performers (q) advance to the Final
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 46.22 | Q | |||
| 2 | align=left | align=left | | 46.25 | Q SB | ||
| 3 | align=left | align=left | | 46.32 | Q SB | ||
| 4 | align=left | align=left | | 46.37 | q | ||
| 5 | align=left | align=left | | 46.58 | Q | ||
| 6 | align=left | align=left | 46.60 | Q | |||
| 7 | align=left | align=left | | 46.83 | q PB | ||
| 8 | align=left | align=left | 46.86 | PB | |||
| 9 | align=left | align=left | 46.86 | ||||
| 10 | align=left | align=left | | 46.88 | |||
| 11 | align=left | align=left |  | 47.19 | |||
| 12 | align=left | align=left | | 47.25 | Q | ||
| 13 | align=left | align=left | | 47.26 | |||
| 14 | align=left | align=left |  | 47.29 | |||
| 15 | align=left | align=left |  | 47.54 | |||
| 16 | align=left | align=left | | 47.61 | |||
| 17 | align=left | align=left |  | 47.64 | |||
| 18 | align=left | align=left |  | 47.83 | |||
| 19 | align=left | align=left | | 47.91 | |||
| 19 | align=left | align=left |  | 47.91 | |||
| 21 | align=left | align=left | | 48.04 |
14 July 2011 / 19:10
| Rank | Name | Nationality | Lane | Reaction Time | Time | Notes | |||
|---|---|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 6 | 0.198 | 46.60 | Q | |||
| 2 | align=left | align=left | | 2 | 0.221 | 47.25 | Q | ||
| 3 | align=left | align=left | | 4 | 0.191 | 47.26 | |||
| 4 | align=left | align=left | | 3 | 0.188 | 47.61 | |||
| 5 | align=left | align=left | | 8 | 0.196 | 47.83 | |||
| 6 | align=left | align=left | | 7 | 0.186 | 47.91 | |||
| 7 | align=left | align=left | | 5 | 0.210 | 48.04 |
14 July 2011 / 19:17
| Rank | Name | Nationality | Lane | Reaction Time | Time | Notes | |||
|---|---|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 6 | 0.242 | 46.22 | Q | |||
| 2 | align=left | align=left | | 4 | 0.181 | 46.32 | Q SB | ||
| 3 | align=left | align=left | | 3 | 0.239 | 46.37 | q | ||
| 4 | align=left | align=left | 7 | 0.189 | 46.86 | PB | |||
| 5 | align=left | align=left | 5 | 0.228 | 46.86 | ||||
| 6 | align=left | align=left | | 8 | 0.140 | 47.54 | |||
| 7 | align=left | align=left | | 2 | 0.199 | 47.91 |
14 July 2011 / 19:24
| Rank | Name | Nationality | Lane | Reaction Time | Time | Notes | |||
|---|---|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 3 | 0.226 | 46.25 | Q SB | ||
| 2 | align=left | align=left | | 4 | 0.172 | 46.58 | Q | ||
| 3 | align=left | align=left | | 8 | 0.174 | 46.83 | q PB | ||
| 4 | align=left | align=left | | 6 | 0.198 | 46.88 | |||
| 5 | align=left | align=left | | 2 | 0.212 | 47.19 | |||
| 6 | align=left | align=left | | 5 | 0.181 | 47.29 | |||
| 7 | align=left | align=left | | 7 | 0.204 | 47.64 |
According to an unofficial count, 21 athletes from 14 countries participated in the event.