| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 1 | 3086 | Karsten WARHOLM |  NOR | 47.30 Q | |
| 2 | 1 | 2 | 1318 | Alison DOS SANTOS |  BRA | 47.31 Q AR | |
| 3 | 2 | 1 | 3907 | Rai BENJAMIN |  USA | 47.37 Q | |
| 4 | 2 | 2 | 3295 | Abderrahman Almoubarrake S ALSALECK |  QAT | 47.47 Q SB | |
| 5 | 3 | 1 | 3668 | Yasmani COPELLO |  TUR | 47.88 q SB | |
| 6 | 3 | 2 | 2439 | Alessandro SIBILIO |  ITA | 47.93 q PB | |
| 7 | 4 | 1 | 2341 | Thomas BARR |  IRL | 48.26 SB | .255 | 
| 8 | 1 | 3 | 2456 | Kyron MCMASTER |  IVB | 48.26 Q | .258 | 
| 9 | 2 | 3 | 1824 | Rasmus MÄGI |  EST | 48.36 Q NR | |
| 10 | 4 | 2 | 3968 | Kenneth SELMON |  USA | 48.58 | |
| 11 | 5 | 2 | 2154 | Luke CAMPBELL |  GER | 48.62 PB | |
| 12 | 3 | 3 | 3939 | David KENDZIERA |  USA | 48.67 | |
| 13 | 6 | 2 | 2626 | Shawn ROWE |  JAM | 48.83 PB | |
| 14 | 5 | 1 | 2611 | Kemar MOWATT |  JAM | 48.95 | |
| 15 | 6 | 1 | 3444 | Sokwakhana ZAZINI |  RSA | 48.99 SB | |
| 16 | 7 | 1 | 1979 | Ludvy VAILLANT |  FRA | 49.02 SB | |
| 17 | 4 | 3 | 2172 | Constantin PREIS |  GER | 49.10 | |
| 18 | 5 | 3 | 1008 | Abdelmalik LAHOULOU |  ALG | 49.14 | |
| 19 | 7 | 2 | 3026 | Nick SMIDT |  NED | 49.35 SB | .348 | 
| 20 | 6 | 3 | 2724 | Hiromu YAMAUCHI |  JPN | 49.35 | .350 | 
| 21 | 7 | 3 | 1958 | Wilfried HAPPIO |  FRA | 49.49 | |
| 22 | 8 | 2 | 1637 | VÃt MÜLLER |  CZE | 49.69 | |
| 23 | 8 | 1 | 2145 | Joshua ABUAKU |  GER | 49.93 | |
| 24 | 8 | 3 | 2592 | Jaheel HYDE |  JAM | 1:27.38 | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second