| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 2 | USA | United States |  USA | 41.56 Q WL | |
| 2 | 1 | 1 | GBR | Great Britain & NI |  GBR | 41.99 Q WL | |
| 3 | 2 | 1 | JAM | Jamaica |  JAM | 42.37 Q SB | |
| 4 | 3 | 1 | GER | Germany |  GER | 42.44 Q SB | |
| 5 | 2 | 2 | ESP | Spain |  ESP | 42.61 Q NR | |
| 6 | 3 | 2 | NGR | Nigeria |  NGR | 42.68 Q SB | |
| 7 | 4 | 2 | ITA | Italy |  ITA | 42.71 q NR | |
| 8 | 5 | 2 | SUI | Switzerland |  SUI | 42.73 q | |
| 9 | 4 | 1 | CHN | PR of China |  CHN | 42.93 SB | |
| 10 | 5 | 1 | CAN | Canada |  CAN | 43.09 | |
| 11 | 6 | 1 | POL | Poland |  POL | 43.19 SB | |
| 12 | 7 | 1 | JPN | Japan |  JPN | 43.33 NR | |
| 13 | 6 | 2 | NED | Netherlands |  NED | 43.46 | .458 | 
| 13 | 6 | 2 | DEN | Denmark |  DEN | 43.46 NR | .458 | 
| 15 | 8 | 2 | ECU | Ecuador |  ECU | 44.17 SB | |
| 16 | 8 | 1 | IRL | Ireland |  IRL | 44.48 | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second