| Pos | Rank | Heat | Bib | Athlete | Mark | Details | Reaction Time | |
|---|---|---|---|---|---|---|---|---|
| 1 | 1 | 5 | 613 | BRN | 49.13  | Q | 0.190 | |
| 2 | 1 | 3 | 1427 | USA | 49.41  | Q | 0.199 | |
| 3 | 2 | 5 | 1045 | JAM | 49.59 PB | Q | 0.181 | |
| 4 | 1 | 6 | 741 | DOM | 49.85  | Q | 0.213 | |
| 5 | 1 | 2 | 935 | HAI | 49.91 NR | Q | 0.202 | |
| 6 | 1 | 4 | 1035 | JAM | 49.91  | Q | 0.201 | |
| 7 | 2 | 6 | 851 | GBR | 49.96  | Q | 0.186 | |
| 8 | 2 | 4 | 1176 | NOR | 50.12  | Q | 0.159 | |
| 9 | 2 | 2 | 1198 | POL | 50.16  | Q | 0.196 | |
| 10 | 1 | 1 | 1144 | NED | 50.32  | Q | 0.194 | |
| 11 | 3 | 4 | 711 | CUB | 50.35 SB | Q | 0.191 | |
| 12 | 3 | 6 | 746 | EGY | 50.36 NR | Q | 0.191 | |
| 13 | 3 | 2 | 1383 | USA | 50.44  | Q | 0.186 | |
| 14 | 4 | 4 | 559 | BAH | 50.53 PB | q | 0.186 | |
| 15 | 2 | 3 | 658 | CHI | 50.61  | Q | 0.185 | |
| 16 | 4 | 6 | 774 | ESP | 50.69 PB | q | 0.172 | |
| 17 | 5 | 4 | 864 | GBR | 50.71  | q | 0.202 | |
| 18 | 3 | 3 | 1096 | KEN | 50.76  | Q | 0.202 | |
| 19 | 2 | 1 | 1451 | USA | 50.82  | Q | 0.185 | |
| 20 | 4 | 2 | 566 | BAR | 50.93  | q | 0.216 | |
| 21 | 3 | 5 | 1249 | ROU | 50.96 SB | Q | 0.175 | |
| 22 | 4 | 3 | 958 | IRL | 51.04  | q | 0.184 | |
| 23 | 3 | 1 | 1034 | JAM | 51.07  | Q | 0.165 | |
| 24 | 4 | 5 | 875 | GBR | 51.37  | q | 0.226 | |
| 25 | 5 | 5 | 1004 | ITA | 51.55  | 0.164 | ||
| 26 | 4 | 1 | 624 | CAN | 51.56  | 0.203 | ||
| 27 | 5 | 2 | 1359 | UGA | 51.61  | 0.261 | ||
| 28 | 5 | 1 | 994 | ITA | 51.70  | 0.162 | ||
| 29 | 5 | 3 | 589 | BER | 51.72  | 0.207 | ||
| 30 | 6 | 3 | 1149 | NED | 51.73  | 0.205 | ||
| 31 | 5 | 6 | 1221 | POL | 51.80  | 0.218 | ||
| 32 | 6 | 5 | 1261 | RSA | 51.82  | 0.174 | ||
| 33 | 6 | 4 | 729 | CZE | 51.90  | 0.243 | ||
| 34 | 6 | 1 | 800 | FIN | 51.92  | 0.179 | ||
| 35 | 7 | 4 | 637 | CAN | 51.98  | 0.187 | ||
| 36 | 7 | 3 | 564 | BAH | 52.00  | 0.201 | ||
| 37 | 6 | 6 | 951 | IRL | 52.19  | 0.209 | ||
| 38 | 6 | 2 | 639 | CAN | 52.19  | 0.185 | ||
| 38 | 6 | 2 | 1155 | NED | 52.19  | 0.208 | ||
| 40 | 7 | 1 | 1463 | ZIM | 52.28  | 0.260 | ||
| 41 | 8 | 1 | 511 | AUS | 52.31  | 0.201 | ||
| 42 | 7 | 5 | 1057 | JPN | 52.41  | 0.211 | ||
| 43 | 8 | 4 | 1245 | PUR | 52.55  | 0.172 | ||
| 44 | 7 | 6 | 704 | CRO | 52.67  | 0.315 | ||
| 45 | 8 | 6 | 552 | AUT | 52.92  | 0.195 | ||
| 46 | 9 | 6 | 1168 | NIG | 52.99 SB | 0.309 | ||
| 47 | 8 | 3 | 604 | BRA | 53.34  | 0.249 | ||
| 48 | 8 | 5 | 1285 | SRI | 53.63  | 0.230 | ||
| 49 | 9 | 5 | 695 | COL | 53.82  | 0.187 | ||
| 50 | 9 | 3 | 649 | CHA | 56.35 PB | 0.268 | ||
| 51 | 8 | 2 | 1253 | RSA | 57.78  | 0.194 |