| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 2 | 3707 | Salwa Eid NASER |  BRN | 50.08 NR | |
| 2 | 2 | 2 | 4330 | Allyson FELIX |  USA | 50.12 | |
| 3 | 1 | 1 | 3654 | Shaunae MILLER-UIBO |  BAH | 50.36 Q | |
| 4 | 1 | 3 | 4331 | Phyllis FRANCIS |  USA | 50.37 | |
| 5 | 2 | 1 | 4037 | Stephenie Ann MCPHERSON |  JAM | 50.56 Q SB | |
| 6 | 3 | 2 | 4054 | Novlene Williams-Mills |  JAM | 50.67 | |
| 7 | 4 | 2 | 4030 | Shericka JACKSON |  JAM | 50.70 | |
| 8 | 3 | 1 | 4341 | Quanera HAYES |  USA | 50.71 | |
| 9 | 2 | 3 | 4027 | Chrisann GORDON-POWELL |  JAM | 50.87 | |
| 10 | 3 | 3 | 3682 | Amantle MONTSHO |  BOT | 51.28 SB | |
| 11 | 4 | 1 | 4097 | Gunta VAIÄŒULE |  LAT | 51.57 | .565 | 
| 12 | 5 | 2 | 3679 | Lydia JELE |  BOT | 51.57 | .566 | 
| 13 | 4 | 3 | 3960 | Ruth Sophia SPELMEYER-PREUß |  GER | 51.77 | |
| 14 | 5 | 3 | 4165 | Iga BAUMGART-WITAN |  POL | 51.81 | .801 | 
| 15 | 6 | 3 | 3885 | Zoey CLARK |  GBR | 51.81 PB | .804 | 
| 16 | 5 | 1 | 3786 | Roxana GÓMEZ |  CUB | 52.01 | |
| 17 | 6 | 1 | 4201 | Bianca Razor |  ROU | 52.09 | |
| 18 | 6 | 2 | 4138 | Yinka AJAYI |  NGR | 52.10 | |
| 19 | 7 | 1 | 4144 | Patience Okon GEORGE |  NGR | 52.60 | |
| 20 | 7 | 2 | 3977 | Eirini VASILEIOU |  GRE | 53.27 | |
| 21 | 8 | 1 | 4021 | Ashley Kelly |  IVB | 54.50 | |
| 2 | 3996 | Sheoran Nirmla |  IND | DQ | |||
| 3 | 4389 | Kabange Mupopo |  ZAM | DQ | |||
| 3 | 4140 | Margaret Bamgbose |  NGR | DQ | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second