The men's 400 metres event at the 2018 African Championships in Athletics was held on 2 and 3 August in Asaba, Nigeria.[1]
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Baboloki Thebe | Thapelo Phora | Chidi Okezie |
Qualification: First 4 of each heat (Q) and the next 4 fastest (q) qualified for the semifinals.
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 5 | 45.94 | Q | |||
| 2 | 5 | 46.02 | Q | |||
| 3 | 5 | 46.24 | Q | |||
| 4 | 3 | 46.33 | Q | |||
| 5 | 1 | 46.45 | Q | |||
| 6 | 5 | 46.55 | Q | |||
| 7 | 3 | 46.69 | Q | |||
| 8 | 2 | 46.75 | Q | |||
| 9 | 3 | 46.82 | Q | |||
| 10 | 2 | 46.94 | Q | |||
| 11 | 4 | 47.04 | Q | |||
| 12 | 1 | 47.12 | Q | |||
| 13 | 2 | 47.22 | Q | |||
| 14 | 4 | Momodou Bah | 47.24 | Q | ||
| 15 | 1 | 47.29 | Q | |||
| 16 | 2 | 47.41 | Q | |||
| 17 | 4 | 47.44 | Q | |||
| 18 | 2 | 47.53 | q | |||
| 19 | 4 | 47.54 | Q | |||
| 19 | 5 | 47.54 | q | |||
| 21 | 3 | 47.69 | Q | |||
| 22 | 4 | 47.84 | q | |||
| 23 | 1 | 47.88 | Q | |||
| 24 | 2 | 47.92 | q | |||
| 25 | 5 | 48.13 | ||||
| 26 | 4 | 48.34 | ||||
| 27 | 3 | 48.41 | ||||
| 28 | 1 | 48.58 | ||||
| 29 | 1 | 48.59 | ||||
| 30 | 5 | 48.64 | ||||
| 31 | 2 | 48.83 | ||||
| 32 | 1 | 48.98 | ||||
| 32 | 3 | 48.98 | ||||
| 34 | 4 | 49.54 | ||||
| 35 | 4 | 49.68 | ||||
| 3 | ||||||
| 1 | ||||||
| 2 | ||||||
| 3 | ||||||
| 5 |
Qualification: First 2 of each semifinal (Q) and the next 2 fastest (q) qualified for the final.
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 2 | 45.76 | Q | |||
| 2 | 3 | 46.09 | Q | |||
| 3 | 2 | 46.10 | Q | |||
| 4 | 3 | 46.14 | Q | |||
| 5 | 1 | 46.25 | Q | |||
| 6 | 3 | 46.35 | q | |||
| 7 | 2 | Momodou Bah | 46.76 | q | ||
| 8 | 1 | 46.79 | Q | |||
| 9 | 1 | 46.84 | ||||
| 10 | 3 | 46.91 | ||||
| 11 | 1 | 46.94 | ||||
| 12 | 3 | 47.11 | ||||
| 13 | 1 | 47.14 | ||||
| 14 | 1 | 47.22 | ||||
| 15 | 2 | 47.32 | ||||
| 16 | 2 | 47.34 | ||||
| 17 | 2 | 47.37 | ||||
| 18 | 2 | 47.76 | ||||
| 19 | 1 | 47.82 | ||||
| 20 | 3 | 47.94 | ||||
| 21 | 2 | 48.02 | ||||
| 22 | 3 | 48.48 | ||||
| 1 | ||||||
| 3 |
| Rank | Lane | Athlete | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 5 | 44.81 | |||||
| 3 | 45.14 | |||||
| 4 | 45.65 | |||||
| 4 | 8 | 46.08 | ||||
| 5 | 6 | 46.38 | ||||
| 6 | 2 | 46.83 | ||||
| 7 | 7 | 47.54 | ||||
| 8 | 1 | Momodou Bah | 47.75 |