| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | 
|---|---|---|---|---|---|---|
| 1 | 1 | 1 | 2410 | Michael NORMAN |  USA | 44.30 Q | 
| 2 | 2 | 1 | 1874 | Matthew HUDSON-SMITH |  GBR | 44.38 Q | 
| 3 | 1 | 3 | 2351 | Champion ALLISON |  USA | 44.71 Q | 
| 4 | 1 | 2 | 1945 | Kirani JAMES |  GRN | 44.74 Q | 
| 5 | 2 | 3 | 2268 | Wayde VAN NIEKERK |  RSA | 44.75 Q | 
| 6 | 3 | 3 | 1566 | Jonathan JONES |  BAR | 44.78 q | 
| 7 | 2 | 2 | 1595 | Bayapo NDORI |  BOT | 44.94 Q | 
| 8 | 3 | 1 | 2041 | Christopher TAYLOR |  JAM | 44.97 q SB | 
| 9 | 3 | 2 | 2437 | Muzala SAMUKONGA |  ZAM | 45.02 PB | 
| 10 | 4 | 3 | 1872 | Alex HAYDOCK-WILSON |  GBR | 45.08 PB | 
| 11 | 4 | 1 | 2264 | Zakithi NENE |  RSA | 45.24 | 
| 12 | 5 | 3 | 1572 | Kévin BORLÉE |  BEL | 45.26 | 
| 13 | 4 | 2 | 2366 | Michael CHERRY |  USA | 45.28 | 
| 14 | 5 | 1 | 1571 | Dylan BORLÉE |  BEL | 45.41 | 
| 15 | 6 | 3 | 2159 | Liemarvin BONEVACIA |  NED | 45.50 | 
| 16 | 7 | 3 | 2080 | Mikhail LITVIN |  KAZ | 45.63 SB | 
| 17 | 5 | 2 | 2069 | Fuga SATO |  JPN | 45.71 | 
| 18 | 6 | 1 | 2075 | Julian Jrummi WALSH |  JPN | 45.75 | 
| 19 | 6 | 2 | 1579 | Alexander DOOM |  BEL | 45.80 | 
| 20 | 7 | 2 | 1979 | Christopher O'DONNELL |  IRL | 46.01 | 
| 21 | 8 | 3 | 1594 | Isaac MAKWALA |  BOT | 46.04 | 
| 22 | 7 | 1 | 1736 | Lidio Andres FELIZ |  DOM | 46.19 | 
| 23 | 8 | 1 | 1526 | Alex BECK |  AUS | 46.21 | 
| 2 | 2014 | Nathon ALLEN |  JAM | DNF |