The women's 400 metres event at the 2002 World Junior Championships in Athletics was held in Kingston, Jamaica, at National Stadium on 16, 17 and 18 July.
| Gold | Monique Henderson | |
| Silver | Sanya Richards | |
| Bronze | Sheryl Morgan |
18 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| align=left | align=left | | 51.10 | ||||
| align=left | align=left | | 51.49 | ||||
| align=left | align=left | | 52.61 | ||||
| 4 | align=left | align=left |  | 52.68 | |||
| 5 | align=left | align=left | 53.20 | ||||
| 6 | align=left | align=left |  | 53.36 | |||
| 7 | align=left | align=left | | 53.76 | |||
| 8 | align=left | align=left | 54.44 |
17 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 52.72 | Q | ||
| 2 | align=left | align=left | | 52.94 | Q | ||
| 3 | align=left | align=left | 53.28 | Q | |||
| 4 | align=left | align=left | 53.30 | Q | |||
| 5 | align=left | align=left | | 53.76 | |||
| 5 | align=left | align=left |  | 53.76 | |||
| 7 | align=left | align=left |  | 54.36 | |||
| 8 | align=left | align=left | 55.13 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 52.31 | Q | ||
| 2 | align=left | align=left | | 53.20 | Q | ||
| 3 | align=left | align=left | | 53.77 | Q | ||
| 4 | align=left | align=left | | 53.80 | Q | ||
| 5 | align=left | align=left | 54.05 | ||||
| 6 | align=left | align=left |  | 54.11 | |||
| 7 | align=left | align=left | | 54.45 | |||
| 8 | align=left | align=left | 55.63 |
16 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 53.46 | Q | ||
| 2 | align=left | align=left | | 54.07 | Q | ||
| 3 | align=left | align=left | 54.18 | Q | |||
| 4 | align=left | align=left | | 54.65 | q | ||
| 5 | align=left | align=left |  | 55.95 | |||
| 6 | align=left | align=left |  | 56.81 | |||
| 7 | align=left | align=left |  | 64.10 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 54.14 | Q | ||
| 2 | align=left | align=left | | 54.69 | Q | ||
| 3 | align=left | align=left | 55.08 | Q | |||
| 4 | align=left | align=left | 55.11 | ||||
| 5 | align=left | align=left | | 55.19 | |||
| 6 | align=left | align=left |  | 56.05 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 52.81 | Q | ||
| 2 | align=left | align=left | 54.12 | Q | |||
| 3 | align=left | align=left | | 54.64 | Q | ||
| 4 | align=left | align=left | 54.96 | q | |||
| 5 | align=left | align=left | | 55.40 | |||
| 6 | align=left | align=left | 55.41 | ||||
| 7 | align=left | align=left | 57.34 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 53.14 | Q | ||
| 2 | align=left | align=left | 54.39 | Q | |||
| 3 | align=left | align=left | | 54.42 | Q | ||
| 4 | align=left | align=left | | 54.47 | q | ||
| 5 | align=left | align=left | | 54.67 | q | ||
| 6 | align=left | align=left |  | 55.36 | |||
| 7 | align=left | align=left | | 55.66 |
According to an unofficial count, 27 athletes from 18 countries participated in the event.