The women's 100 metres hurdles event at the 2004 World Junior Championships in Athletics was held in Grosseto, Italy, at Stadio Olimpico Carlo Zecchini on 15 and 16 July.
| Gold | Ronetta Alexander | |
| Silver | Sabrina Altermatt | |
| Bronze | Stephanie Lichtl |
16 July
Wind: -1.0 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| align=left | align=left | | 13.28 | ||||
| align=left | align=left | 13.39 | |||||
| align=left | align=left | 13.40 | |||||
| 4 | align=left | align=left |  | 13.41 | |||
| 5 | align=left | align=left |  | 13.58 | |||
| 6 | align=left | align=left | 13.62 | ||||
| 7 | align=left | align=left |  | 13.69 | |||
| 8 | align=left | align=left |  | 14.69 |
16 July
Wind: -0.3 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 13.38 | Q | ||
| 2 | align=left | align=left | 13.45 | Q | |||
| 3 | align=left | align=left | 13.48 | Q | |||
| 4 | align=left | align=left | 13.60 | Q | |||
| 5 | align=left | align=left |  | 13.60 | |||
| 6 | align=left | align=left |  | 13.92 | |||
| 7 | align=left | align=left |  | 13.94 | |||
| 8 | align=left | align=left | 14.28 |
Wind: -0.9 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 13.42 | Q | ||
| 2 | align=left | align=left | | 13.49 | Q | ||
| 3 | align=left | align=left | | 13.51 | Q | ||
| 4 | align=left | align=left | | 13.59 | Q | ||
| 5 | align=left | align=left | | 13.60 | |||
| 6 | align=left | align=left | | 13.83 | |||
| 7 | align=left | align=left |  | 13.95 | |||
| 8 | align=left | align=left | | 14.16 |
15 July
Wind: +1.0 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 13.30 | Q | ||
| 2 | align=left | align=left | 13.36 | Q | |||
| 3 | align=left | align=left | | 13.54 | Q | ||
| 4 | align=left | align=left | 13.91 | q | |||
| 5 | align=left | align=left |  | 13.92 | |||
| 6 | align=left | align=left |  | 13.98 | |||
| 7 | align=left | align=left |  | 14.12 | |||
| 8 | align=left | align=left |  | 14.34 |
Wind: -0.4 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 13.43 | Q | ||
| 2 | align=left | align=left | | 13.70 | Q | ||
| 3 | align=left | align=left | | 13.93 | Q | ||
| 4 | align=left | align=left | 14.03 | ||||
| 5 | align=left | align=left |  | 14.04 | |||
| 6 | align=left | align=left |  | 14.27 | |||
| 7 | align=left | align=left |  | 14.28 |
Wind: +0.4 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 13.46 | Q | ||
| 2 | align=left | align=left | | 13.74 | Q | ||
| 3 | align=left | align=left | | 13.75 | Q | ||
| 4 | align=left | align=left | | 13.93 | |||
| 5 | align=left | align=left | | 14.07 | |||
| 6 | align=left | align=left | | 14.09 | |||
| 7 | align=left | align=left | | 14.98 | |||
| 8 | align=left | align=left |  | 15.31 |
Wind: +0.2 m/s
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 13.53 | Q | |||
| 2 | align=left | align=left | | 13.56 | Q | ||
| 3 | align=left | align=left | | 13.59 | Q | ||
| 4 | align=left | align=left | 13.60 | q | |||
| 5 | align=left | align=left | | 13.62 | q | ||
| 6 | align=left | align=left | | 13.85 | q | ||
| 7 | align=left | align=left | | 14.22 |
According to an unofficial count, 30 athletes from 21 countries participated in the event.