The women's 400 metres hurdles at the 2012 World Junior Championships in Athletics was held at the Estadi Olímpic Lluís Companys on 12, 13, and 14 July.[1]
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Janieve Russell | Aurèlie Chaboudez | Kaila Barber |
, the existing world junior and championship records were as follows.
| World Junior Record | 54.40 | Nanjing, China | 21 October 2005 | ||
| Championship Record | 54.70 | Kingston, Jamaica | 19 July 2002 | ||
| World Junior Leading | 57.04 | Kingston, Jamaica | 28 June 2012 | ||
| Broken records during the 2012 World Junior Championships in Athletics | |||||
|---|---|---|---|---|---|
| World Junior Leading | 56.62 | Barcelona, Spain | 14 July 2012 | ||
Qualification: first 4 of each heat (Q) plus the 4 fastest times (q) qualified
| Rank | Heat | Lane | Name | Nationality | Time | Note | |
|---|---|---|---|---|---|---|---|
| 1 | 1 | 7 | 58.01 | Q | |||
| 2 | 2 | 8 | 58.40 | Q | |||
| 3 | 1 | 2 | 58.46 | Q, PB | |||
| 4 | 4 | 3 | 58.57 | Q | |||
| 5 | 2 | 4 | 58.99 | Q, PB | |||
| 5 | 1 | 8 | 58.99 | Q | |||
| 7 | 1 | 9 | 59.15 | Q, PB | |||
| 8 | 1 | 4 | 59.20 | q, PB | |||
| 9 | 3 | 8 | 59.28 | Q | |||
| 10 | 4 | 4 | 59.31 | Q | |||
| 11 | 5 | 8 | 59.38 | Q | |||
| 12 | 5 | 9 | 59.56 | Q | |||
| 13 | 4 | 9 | 59.66 | Q | |||
| 14 | 4 | 8 | 59.74 | Q | |||
| 15 | 2 | 9 | 59.84 | Q | |||
| 16 | 1 | 6 | 1:00.01 | q, PB | |||
| 17 | 2 | 7 | 1:00.02 | Q | |||
| 18 | 3 | 5 | 1:00.06 | Q | |||
| 19 | 5 | 3 | 1:00.13 | Q | |||
| 20 | 5 | 5 | 1:00.14 | Q | |||
| 21 | 2 | 6 | 1:00.19 | q | |||
| 22 | 4 | 7 | 1:00.56 | q | |||
| 23 | 5 | 6 | 1:00.63 | ||||
| 24 | 3 | 7 | 1:00.72 | Q | |||
| 25 | 3 | 3 | 1:00.73 | Q | |||
| 26 | 3 | 9 | 1:00.83 | ||||
| 27 | 1 | 5 | 1:00.93 | ||||
| 28 | 5 | 7 | 1:01.06 | ||||
| 29 | 4 | 6 | 1:01.09 | ||||
| 30 | 4 | 5 | 1:01.14 | ||||
| 31 | 2 | 3 | 1:01.28 | ||||
| 32 | 2 | 5 | 1:02.01 | SB | |||
| 33 | 5 | 4 | 1:02.04 | ||||
| 34 | 1 | 3 | 1:03.88 | ||||
| 35 | 3 | 6 | 1:04.42 | ||||
| 36 | 2 | 2 | 1:10.26 | ||||
| 3 | 4 | DNS |
Qualification: The first 2 of each heat (Q) and the 2 fastest times (q) qualified
| Rank | Heat | Lane | Name | Nationality | Time | Note | |
|---|---|---|---|---|---|---|---|
| 1 | 3 | 4 | 57.23 | Q | |||
| 2 | 2 | 8 | 57.29 | Q, PB | |||
| 3 | 2 | 7 | 57.34 | Q, NJ | |||
| 4 | 1 | 5 | 57.35 | Q, PB | |||
| 5 | 2 | 6 | 57.45 | q, NJ | |||
| 6 | 3 | 5 | 57.46 | Q, SB | |||
| 6 | 1 | 3 | 57.46 | Q | |||
| 8 | 1 | 4 | 57.82 | q, PB | |||
| 9 | 1 | 6 | 57.96 | ||||
| 10 | 2 | 5 | 58.04 | PB | |||
| 11 | 3 | 7 | 58.13 | PB | |||
| 12 | 3 | 8 | 58.60 | PB | |||
| 13 | 3 | 3 | 58.82 | ||||
| 14 | 3 | 6 | 58.93 | ||||
| 15 | 1 | 2 | 59.42 | ||||
| 16 | 2 | 4 | 59.75 | ||||
| 17 | 3 | 2 | 59.88 | PB | |||
| 18 | 1 | 7 | 59.94 | ||||
| 19 | 1 | 9 | 59.95 | ||||
| 20 | 1 | 8 | 1:00.40 | ||||
| 21 | 2 | 9 | 1:00.63 | ||||
| 22 | 2 | 3 | 1:00.91 | ||||
| 23 | 2 | 2 | 1:00.97 | ||||
| 24 | 3 | 9 | 1:03.88 |
| Rank | Lane | Name | Nationality | Time | Note | |
|---|---|---|---|---|---|---|
| 6 | 56.62 | WJL | ||||
| 9 | 57.14 | NJ | ||||
| 4 | 57.63 | |||||
| 4 | 7 | 58.10 | ||||
| 5 | 2 | 58.35 | ||||
| 6 | 5 | 58.45 | ||||
| 7 | 3 | 58.77 | ||||
| 8 | DNF |
According to an unofficial count, 36 athletes from 26 countries participated in the event.