The men's 400 metres hurdles at the 2012 World Junior Championships in Athletics was held at the Estadi Olímpic Lluís Companys on 11–13 July.[1]
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Eric Futch | Takahiro Matsumoto | Ibrahim Mohammed Saleh |
, the existing world junior and championship records were as follows.
| World Junior Record | 48.02 | Los Angeles, United States | 17 June 1984 | ||
| Championship Record | 48.51 | Grosseto, Italy | 16 July 2004 | ||
| World Junior Leading | 50.48 | Regensburg, Germany | 2 June 2012 | ||
| Broken records during the 2012 World Junior Championships in Athletics | |||||
|---|---|---|---|---|---|
| World Junior Leading | 50.24 | Barcelona, Spain | 13 July 2012 | ||
Qualification: first 3 of each heat (Q) plus the 3 fastest times (q) qualified
| Rank | Heat | Lane | Name | Nationality | Time | Note | |
|---|---|---|---|---|---|---|---|
| 1 | 7 | 3 | 50.95 | Q, PB | |||
| 2 | 1 | 5 | 51.16 | Q, PB | |||
| 3 | 4 | 9 | 51.26 | Q, SB | |||
| 4 | 3 | 5 | 51.36 | Q | |||
| 5 | 4 | 4 | 51.40 | Q | |||
| 6 | 7 | 9 | 51.52 | Q | |||
| 7 | 1 | 6 | 51.65 | Q | |||
| 8 | 6 | 9 | 51.67 | Q | |||
| 9 | 3 | 9 | 51.68 | Q, PB | |||
| 10 | 1 | 3 | 51.78 | Q | |||
| 11 | 5 | 6 | 51.82 | Q | |||
| 12 | 7 | 8 | 51.82 | Q, SB | |||
| 13 | 6 | 6 | 51.93 | Q, PB | |||
| 14 | 3 | 4 | 51.99 | Q | |||
| 15 | 2 | 8 | 52.01 | Q | |||
| 16 | 3 | 6 | 52.16 | q, SB | |||
| 17 | 6 | 3 | 52.21 | Q | |||
| 18 | 2 | 9 | 52.27 | Q | |||
| 19 | 5 | 8 | 52.29 | Q | |||
| 20 | 5 | 7 | 52.31 | Q | |||
| 21 | 6 | 4 | 52.37 | q | |||
| 22 | 5 | 9 | 52.39 | q, PB | |||
| 23 | 1 | 8 | 52.41 | ||||
| 24 | 2 | 2 | 52.42 | Q | |||
| 25 | 4 | 8 | 52.44 | Q | |||
| 26 | 1 | 7 | 52.56 | ||||
| 27 | 3 | 7 | 52.56 | ||||
| 28 | 5 | 5 | 52.61 | ||||
| 29 | 2 | 3 | 52.71 | PB | |||
| 30 | 7 | 2 | 52.71 | ||||
| 31 | 1 | 9 | 52.73 | PB | |||
| 32 | 4 | 6 | 52.77 | ||||
| 33 | 7 | 5 | 52.78 | ||||
| 34 | 4 | 2 | 52.85 | ||||
| 35 | 7 | 6 | 52.94 | ||||
| 36 | 2 | 4 | 52.95 | ||||
| 37 | 7 | 7 | 53.00 | PB | |||
| 38 | 4 | 5 | 53.06 | ||||
| 39 | 3 | 8 | 53.11 | ||||
| 40 | 3 | 3 | 53.26 | ||||
| 41 | 1 | 4 | 53.29 | ||||
| 42 | 2 | 6 | 53.29 | SB | |||
| 43 | 6 | 5 | 53.43 | ||||
| 44 | 2 | 5 | 53.46 | ||||
| 45 | 2 | 7 | 53.50 | ||||
| 46 | 5 | 3 | 53.74 | ||||
| 47 | 4 | 3 | 53.90 | ||||
| 48 | 7 | 4 | 54.03 | SB | |||
| 49 | 6 | 8 | 54.13 | ||||
| 50 | 4 | 7 | 54.51 | ||||
| 51 | 5 | 4 | 55.65 | ||||
| 52 | 6 | 7 | 57.21 |
Qualification: The first 2 of each heat (Q) and the 2 fastest times (q) qualified
| Rank | Heat | Lane | Name | Nationality | Time | Note | |
|---|---|---|---|---|---|---|---|
| 1 | 2 | 6 | 50.45 | Q, WJL | |||
| 2 | 1 | 9 | 50.66 | Q | |||
| 3 | 1 | 4 | 50.76 | Q, PB | |||
| 4 | 3 | 6 | 50.77 | Q | |||
| 5 | 2 | 9 | 50.80 | Q, PB | |||
| 6 | 3 | 5 | 50.81 | Q, PB | |||
| 7 | 1 | 7 | 50.89 | q, PB | |||
| 8 | 1 | 6 | 51.11 | q, PB | |||
| 9 | 2 | 5 | 51.12 | ||||
| 10 | 3 | 7 | 51.15 | ||||
| 11 | 1 | 5 | 51.18 | ||||
| 12 | 3 | 4 | 51.36 | NJ | |||
| 13 | 3 | 9 | 51.43 | PB | |||
| 14 | 3 | 8 | 51.51 | PB | |||
| 14 | 3 | 2 | 51.51 | PB | |||
| 16 | 1 | 8 | 51.52 | ||||
| 17 | 2 | 3 | 51.65 | ||||
| 18 | 1 | 2 | 51.70 | ||||
| 19 | 2 | 7 | 51.93 | ||||
| 20 | 3 | 3 | 52.33 | ||||
| 21 | 1 | 3 | 52.51 | ||||
| 22 | 2 | 8 | 52.67 | ||||
| 23 | 2 | 2 | 53.06 | ||||
| – | 2 | 4 | DNF |
| Rank | Lane | Name | Nationality | Time | Note | |
|---|---|---|---|---|---|---|
| 6 | 50.24 | WJL | ||||
| 5 | 50.41 | PB | ||||
| 4 | 50.47 | PB | ||||
| 4 | 7 | 50.49 | ||||
| 5 | 3 | 50.80 | ||||
| 6 | 9 | 50.80 | PB | |||
| 7 | 8 | 51.17 | ||||
| 8 | 2 | 51.26 |
According to an unofficial count, 52 athletes from 36 countries participated in the event.