| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 1 | 445 | Shaunae MILLER-UIBO |  BAH | 49.55 Q SB | |
| 2 | 1 | 3 | 593 | Marileidy PAULINO |  DOM | 49.98 Q | |
| 3 | 2 | 1 | 844 | Candice MCLEOD |  JAM | 50.05 Q SB | |
| 4 | 2 | 3 | 449 | Sada WILLIAMS |  BAR | 50.12 Q SB | |
| 5 | 1 | 2 | 590 | Fiordaliza COFIL |  DOM | 50.14 Q PB | |
| 6 | 2 | 2 | 952 | Lieke KLAVER |  NED | 50.18 Q NR | |
| 7 | 3 | 2 | 845 | Stephenie Ann MCPHERSON |  JAM | 50.56 q | |
| 8 | 3 | 1 | 1012 | Anna KIEŁBASIŃSKA |  POL | 50.65 q | |
| 9 | 4 | 1 | 782 | Rhasidat ADELEKE |  IRL | 50.81 | |
| 10 | 3 | 3 | 1154 | Talitha DIGGS |  USA | 50.84 | |
| 11 | 5 | 1 | 708 | Victoria OHURUOGU |  GBR | 50.99 PB | |
| 12 | 6 | 1 | 1174 | Lynna IRBY-JACKSON |  USA | 51.00 | |
| 13 | 4 | 3 | 564 | Roxana GÓMEZ |  CUB | 51.12 | |
| 14 | 4 | 2 | 721 | Nicole YEARGIN |  GBR | 51.22 | |
| 15 | 5 | 2 | 1011 | Natalia KACZMAREK |  POL | 51.34 | |
| 16 | 5 | 3 | 863 | Charokee YOUNG |  JAM | 51.41 | |
| 17 | 6 | 3 | 580 | Lada VONDROVÁ |  CZE | 51.47 | |
| 18 | 6 | 2 | 774 | Aliyah ABRAMS |  GUY | 51.79 | .783 | 
| 19 | 7 | 1 | 1026 | Cátia AZEVEDO |  POR | 51.79 | .785 | 
| 20 | 7 | 2 | 1041 | Gabby SCOTT |  PUR | 51.97 | |
| 21 | 7 | 3 | 926 | Modesta Justė MORAUSKAITĖ |  LTU | 52.19 | |
| 22 | 8 | 3 | 711 | Ama PIPI |  GBR | 52.28 | |
| 23 | 8 | 2 | 438 | Susanne GOGL-WALLI |  AUT | 52.37 | |
| 24 | 8 | 1 | 485 | Tabata VITORINO |  BRA | 52.42 | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second