The men's 400 metres hurdles event at the 2005 European Athletics U23 Championships was held in Erfurt, Germany, at Steigerwaldstadion on 15 and 16 July.
| Gold | Rhys Williams | |
| Silver | Minas Alozidis | |
| Bronze | Ákos Dezső |
16 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| align=left | align=left | 49.60 | |||||
| align=left | align=left | 50.04 | |||||
| align=left | align=left | | 50.31 | ||||
| 4 | align=left | align=left |  | 50.39 | |||
| 5 | align=left | align=left |  | 50.96 | |||
| 6 | align=left | align=left |  | 51.45 | |||
| 7 | align=left | align=left |  | 51.47 | |||
| align=left | align=left | DNF |
15 July
Qualified: first 2 in each heat and 2 best to the Final
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 50.68 | Q | |||
| 2 | align=left | align=left | | 50.92 | Q | ||
| 3 | align=left | align=left | 51.05 | q | |||
| 4 | align=left | align=left |  | 51.58 | |||
| 5 | align=left | align=left | | 51.95 | |||
| 6 | align=left | align=left | 52.22 | ||||
| 7 | align=left | align=left | 52.43 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 51.01 | Q | ||
| 2 | align=left | align=left | | 51.60 | Q | ||
| 3 | align=left | align=left | | 51.83 | |||
| 4 | align=left | align=left | 51.94 | ||||
| 5 | align=left | align=left |  | 52.03 | |||
| 6 | align=left | align=left |  | 54.31 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 50.34 | Q | |||
| 2 | align=left | align=left | | 50.79 | Q | ||
| 3 | align=left | align=left | | 51.36 | q | ||
| 4 | align=left | align=left | | 51.76 | |||
| 5 | align=left | align=left | | 51.87 | |||
| 6 | align=left | align=left |  | 53.09 |
According to an unofficial count, 19 athletes from 15 countries participated in the event.
(1) (1) (1) (1) (2) (2) (2) (1) (2)