| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 6 | 1684 | Marileidy PAULINO | 
 DOM                 | 
                50.06 Q | |
| 2 | 1 | 1 | 1131 | Shaunae MILLER-UIBO | 
 BAH                 | 
                50.50 Q | |
| 3 | 2 | 1 | 1583 | Roxana GÓMEZ | 
 CUB                 | 
                50.76 Q =PB | |
| 4 | 1 | 3 | 3847 | Allyson FELIX | 
 USA                 | 
                50.84 Q | |
| 5 | 1 | 5 | 2502 | Stephenie Ann MCPHERSON | 
 JAM                 | 
                50.89 Q | |
| 6 | 2 | 6 | 3857 | Wadeline JONATHAS | 
 USA                 | 
                50.93 Q | |
| 7 | 1 | 2 | 2033 | Jodie WILLIAMS | 
 GBR                 | 
                50.99 Q | |
| 8 | 2 | 5 | 3164 | Natalia KACZMAREK | 
 POL                 | 
                51.06 Q | |
| 9 | 2 | 2 | 3853 | Quanera HAYES | 
 USA                 | 
                51.07 Q | |
| 10 | 1 | 4 | 2501 | Candice MCLEOD | 
 JAM                 | 
                51.09 Q | |
| 11 | 2 | 3 | 2500 | Roneisha MCGREGOR | 
 JAM                 | 
                51.14 Q | .138 | 
| 12 | 3 | 3 | 1629 | Lada VONDROVÁ | 
 CZE                 | 
                51.14 Q PB | .139 | 
| 13 | 4 | 3 | 2021 | Ama PIPI | 
 GBR                 | 
                51.17 q | |
| 14 | 3 | 5 | 2924 | Paola MORÁN | 
 MEX                 | 
                51.18 Q SB | |
| 15 | 3 | 2 | 3223 | Cátia AZEVEDO | 
 POR                 | 
                51.26 Q | |
| 16 | 3 | 1 | 1151 | Sada WILLIAMS | 
 BAR                 | 
                51.36 Q SB | |
| 17 | 3 | 6 | 2995 | Lieke KLAVER | 
 NED                 | 
                51.37 Q | |
| 18 | 4 | 1 | 2249 | Aliyah ABRAMS | 
 GUY                 | 
                51.44 q SB | |
| 19 | 2 | 4 | 1920 | Amandine BROSSIER | 
 FRA                 | 
                51.65 Q | |
| 20 | 4 | 2 | 2991 | Lisanne DE WITTE | 
 NED                 | 
                51.68 q SB | |
| 21 | 5 | 1 | 1388 | Kyra CONSTANTINE | 
 CAN                 | 
                51.69 q | |
| 22 | 4 | 6 | 1762 | Aauri Lorena BOKESA | 
 ESP                 | 
                51.89 q SB | |
| 23 | 5 | 6 | 1606 | Eleni ARTYMATA | 
 CYP                 | 
                51.91 q | |
| 24 | 4 | 5 | 2333 | Phil HEALY | 
 IRL                 | 
                51.98 | |
| 25 | 5 | 3 | 1301 | Tiffani MARINHO | 
 BRA                 | 
                52.11 | |
| 26 | 3 | 4 | 1112 | Susanne GOGL-WALLI | 
 AUT                 | 
                52.19 Q | |
| 27 | 4 | 4 | 2137 | Corinna SCHWAB | 
 GER                 | 
                52.29 | |
| 28 | 6 | 1 | 3462 | Anita HORVAT | 
 SLO                 | 
                52.34 | |
| 29 | 5 | 2 | 1066 | Bendere OBOYA | 
 AUS                 | 
                52.37 | |
| 30 | 7 | 1 | 3046 | Patience Okon GEORGE | 
 NGR                 | 
                52.41 | |
| 31 | 6 | 3 | 3707 | Leni SHIDA | 
 UGA                 | 
                52.48 | |
| 32 | 5 | 5 | 2757 | Hellen Syombua KALII | 
 KEN                 | 
                52.70 | |
| 33 | 6 | 5 | 2863 | Agnė ŠERKŠNIENĖ | 
 LTU                 | 
                52.78 | |
| 34 | 6 | 6 | 1624 | Barbora MALÍKOVÁ | 
 CZE                 | 
                52.83 | |
| 35 | 5 | 4 | 2218 | Eirini VASILEIOU | 
 GRE                 | 
                53.16 | |
| 36 | 7 | 5 | 1400 | Natassha MCDONALD | 
 CAN                 | 
                53.54 | |
| 37 | 7 | 6 | 1450 | Shalysa WRAY | 
 CAY                 | 
                53.61 | |
| 38 | 8 | 6 | 1266 | Christine BOTLOGETSWE | 
 BOT                 | 
                53.99 SB | |
| 39 | 7 | 3 | 1226 | Samantha DIRKS | 
 BIZ                 | 
                54.16 SB | |
| 40 | 8 | 3 | 3748 | Tetyana MELNYK | 
 UKR                 | 
                54.99 | |
| 41 | 6 | 4 | 1268 | Galefele MOROKO | 
 BOT                 | 
                55.89 SB | |
| 2 | 1267 | Amantle MONTSHO | 
 BOT                 | 
                DNF | |||
| 2 | 2234 | Meleni RODNEY | 
 GRN                 | 
                DNF | |||
| 2 | 2660 | Aliya BOSHNAK | 
 JOR                 | 
                DQ | |||
| 4 | 2034 | Nicole YEARGIN | 
 GBR                 | 
                DQ | |||
| 4 | 1174 | Cynthia BOLINGO | 
 BEL                 | 
                DNS | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second