| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 2 | 202 | Óscar HUSILLOS |  ESP | 45.69 Q NIR | |
| 2 | 2 | 2 | 407 | Michael CHERRY |  USA | 45.73 Q | |
| 3 | 1 | 1 | 188 | Luguelín SANTOS |  DOM | 46.31 Q SB | |
| 4 | 1 | 3 | 173 | Pavel MASLÁK |  CZE | 46.32 Q | |
| 5 | 2 | 1 | 401 | Aldrich BAILEY JR |  USA | 46.33 Q | .327 | 
| 6 | 2 | 3 | 386 | Deon LENDORE |  TTO | 46.33 Q | .330 | 
| 7 | 3 | 3 | 365 | Luka JANEŽIČ |  SLO | 46.37 | |
| 8 | 3 | 2 | 344 | Rafał Omelko |  POL | 46.39 | |
| 9 | 3 | 1 | 339 | Jakub KRZEWINA |  POL | 46.69 | |
| 10 | 4 | 1 | 281 | Javon FRANCIS |  JAM | 46.73 | |
| 11 | 4 | 2 | 189 | Juander SANTOS |  DOM | 46.83 PB | |
| 12 | 5 | 2 | 385 | Asa GUEVARA |  TTO | 46.91 | |
| 13 | 5 | 1 | 172 | Patrik ŠORM |  CZE | 47.04 | |
| 14 | 6 | 2 | 231 | Lee THOMPSON |  GBR | 47.14 | .136 | 
| 15 | 6 | 1 | 197 | Lucas BÚA |  ESP | 47.14 | .140 | 
| 16 | 4 | 3 | 293 | Mikhail LITVIN |  KAZ | 47.94 | |
| 17 | 5 | 3 | 324 | Chidi OKEZIE |  NGR | 48.53 | |
| 3 | 304 | Yousef KARAM |  KUW | DNF | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second