| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 2 | 222 | Steven GARDINER |  BAH | 44.13 Q SB | |
| 2 | 2 | 2 | 1001 | Kirani JAMES |  GRN | 44.23 Q SB | |
| 3 | 1 | 1 | 1903 | Fred KERLEY |  USA | 44.25 Q | |
| 4 | 2 | 1 | 1288 | Emmanuel Kipkurui KORIR |  KEN | 44.37 Q SB | |
| 5 | 1 | 3 | 1749 | Machel CEDENIO |  TTO | 44.41 Q SB | |
| 6 | 2 | 3 | 536 | Anthony José ZAMBRANO |  COL | 44.55 Q NR | |
| 7 | 3 | 2 | 1158 | Demish GAYE |  JAM | 44.66 q SB | |
| 8 | 3 | 3 | 1154 | Akeem BLOOMFIELD |  JAM | 44.77 q | |
| 9 | 3 | 1 | 1096 | Davide RE |  ITA | 44.85 | |
| 10 | 4 | 2 | 1921 | Vernon NORWOOD |  USA | 45.00 | .992 | 
| 11 | 5 | 2 | 305 | Leungo SCOTCH |  BOT | 45.00 PB | .996 | 
| 12 | 4 | 1 | 244 | Jonathan SACOOR |  BEL | 45.03 PB | |
| 13 | 4 | 3 | 1217 | Julian Jrummi WALSH |  JPN | 45.13 PB | |
| 14 | 5 | 3 | 830 | Rabah YOUSIF |  GBR | 45.15 SB | |
| 15 | 6 | 2 | 535 | Jhon Alejandro PERLAZA |  COL | 45.17 | |
| 16 | 5 | 1 | 1637 | Thapelo PHORA |  RSA | 45.24 | |
| 17 | 6 | 1 | 360 | Abbas Abubakar ABBAS |  BRN | 45.26 | |
| 18 | 7 | 1 | 1931 | Nathan STROTHER |  USA | 45.34 | |
| 19 | 7 | 2 | 414 | Philip Osei |  CAN | 45.44 | |
| 20 | 8 | 2 | 154 | Steven SOLOMON |  AUS | 45.54 SB | |
| 21 | 6 | 3 | 1286 | Alphas Leken KISHOYIAN |  KEN | 45.55 | |
| 22 | 7 | 3 | 1920 | Michael NORMAN |  USA | 45.94 | |
| 23 | 8 | 1 | 1336 | Mazen Mawtan AL YASEN |  KSA | 46.11 | |
| 3 | 1338 | Yousef KARAM |  KUW | DNF | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second