The men's 400 metres hurdles event at the 1998 World Junior Championships in Athletics was held in Annecy, France, at Parc des Sports on 28, 29 and 31 July.
| Gold | Periklís Iakovákis | |
| Silver | Osiris Martínez | |
| Bronze | Peter Bate |
31 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| align=left | align=left | 49.82 | |||||
| align=left | align=left | | 50.17 | ||||
| align=left | align=left | | 50.83 | ||||
| 4 | align=left | align=left |  | 50.98 | |||
| 5 | align=left | align=left |  | 50.99 | |||
| 6 | align=left | align=left | 51.20 | ||||
| 7 | align=left | align=left |  | 51.41 | |||
| 8 | align=left | align=left | 52.04 |
29 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 50.45 | Q | ||
| 2 | align=left | align=left | 50.47 | Q | |||
| 3 | align=left | align=left | | 51.10 | Q | ||
| 4 | align=left | align=left | 51.35 | q | |||
| 5 | align=left | align=left | | 51.47 | q | ||
| 6 | align=left | align=left | 52.12 | ||||
| 7 | align=left | align=left | 52.13 | ||||
| 8 | align=left | align=left |  | 52.15 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 50.50 | Q | ||
| 2 | align=left | align=left | 50.73 | Q | |||
| 3 | align=left | align=left | | 51.11 | Q | ||
| 4 | align=left | align=left |  | 51.55 | |||
| 5 | align=left | align=left | | 51.89 | |||
| 6 | align=left | align=left |  | 52.03 | |||
| 7 | align=left | align=left |  | 52.04 | |||
| 8 | align=left | align=left |  | 52.71 |
28 July
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 52.03 | Q | ||
| 2 | align=left | align=left | | 52.20 | Q | ||
| 3 | align=left | align=left |  | 52.66 | |||
| 4 | align=left | align=left |  | 52.68 | |||
| 5 | align=left | align=left |  | 53.42 | |||
| 6 | align=left | align=left |  | 53.60 | |||
| 7 | align=left | align=left | 54.42 | ||||
| 8 | align=left | align=left |  | 58.19 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 51.99 | Q | |||
| 2 | align=left | align=left | | 52.31 | Q | ||
| 3 | align=left | align=left | | 52.80 | |||
| 4 | align=left | align=left | | 53.02 | |||
| 5 | align=left | align=left |  | 53.46 | |||
| 6 | align=left | align=left |  | 54.38 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 50.93 | Q | ||
| 2 | align=left | align=left | | 52.00 | Q | ||
| 3 | align=left | align=left | | 52.06 | q | ||
| 4 | align=left | align=left | 52.88 | ||||
| 5 | align=left | align=left | 53.04 | ||||
| 6 | align=left | align=left | | 53.67 | |||
| 7 | align=left | align=left |  | 53.79 | |||
| 8 | align=left | align=left | 54.93 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 51.43 | Q | |||
| 2 | align=left | align=left | | 52.22 | Q | ||
| 3 | align=left | align=left | 52.25 | q | |||
| 4 | align=left | align=left | | 52.46 | q | ||
| 5 | align=left | align=left |  | 52.72 | |||
| 6 | align=left | align=left | 52.78 | ||||
| 7 | align=left | align=left | | 53.00 | |||
| 8 | align=left | align=left |  | 58.12 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 51.61 | Q | ||
| 2 | align=left | align=left | 51.64 | Q | |||
| 3 | align=left | align=left | | 52.10 | q | ||
| 4 | align=left | align=left | | 52.11 | q | ||
| 5 | align=left | align=left | 52.33 | q | |||
| 6 | align=left | align=left |  | 52.61 | |||
| 7 | align=left | align=left | | 54.98 | |||
| 8 | align=left | align=left | | 60.62 |
According to an unofficial count, 38 athletes from 28 countries participated in the event.