| Pos | Rank | Heat | Bib | Athlete | Mark | Details | Reaction Time | |
|---|---|---|---|---|---|---|---|---|
| 1 | 1 | 3 | 1427 | USA | 48.29 WL | Q | 0.212 | |
| 2 | 2 | 3 | 851 | GBR | 49.38 SB | Q | 0.195 | |
| 3 | 3 | 3 | 1035 | JAM | 49.46 SB | q | 0.191 | |
| 4 | 1 | 2 | 613 | BRN | 49.47  | Q | 0.199 | |
| 5 | 1 | 1 | 1198 | POL | 49.67 SB | Q | 0.203 | |
| 6 | 2 | 2 | 711 | CUB | 49.78 SB | Q | 0.223 | |
| 7 | 2 | 1 | 741 | DOM | 49.82  | Q | 0.210 | |
| 8 | 3 | 1 | 1176 | NOR | 49.87  | q | 0.176 | |
| 9 | 4 | 3 | 658 | CHI | 49.88  | 0.197 | ||
| 10 | 3 | 2 | 1451 | USA | 50.20  | 0.194 | ||
| 11 | 4 | 2 | 1144 | NED | 50.25  | 0.243 | ||
| 12 | 5 | 2 | 1045 | JAM | 50.39  | 0.191 | ||
| 13 | 4 | 1 | 566 | BAR | 50.39 SB | 0.185 | ||
| 14 | 5 | 1 | 1383 | USA | 50.63  | 0.161 | ||
| 15 | 6 | 1 | 935 | HAI | 50.67  | 0.202 | ||
| 16 | 5 | 3 | 746 | EGY | 50.69  | 0.196 | ||
| 17 | 6 | 2 | 559 | BAH | 50.81  | 0.184 | ||
| 18 | 6 | 3 | 1249 | ROU | 50.90 SB | 0.167 | ||
| 19 | 7 | 3 | 774 | ESP | 50.97  | 0.180 | ||
| 20 | 8 | 3 | 958 | IRL | 51.22  | 0.200 | ||
| 21 | 7 | 2 | 1096 | KEN | 51.36  | 0.251 | ||
| 22 | 7 | 1 | 1034 | JAM | 51.42  | 0.179 | ||
| 23 | 8 | 1 | 864 | GBR | 51.51  | 0.236 | ||
| 24 | 8 | 2 | 875 | GBR | 51.65  | 0.232 |