Semifinal 1
lundi 7 août 2017, 21h55 GMT – 21h55 GMT
| Nom | Équipe | Temps | |
|---|---|---|---|
| 1 |  Shaunae Miller-Uibo | Bahamas | 50.36″ |
| 2 |  Stephenie McPherson | Jamaica | + 0.2″ |
| 3 |  Quanera Hayes | United States | + 0.35″ |
| 4 |  Gunta Vaicule | Latvia | + 1.21″ |
| 5 | Roxana Gómez | Cuba | + 1.65″ |
| 6 |  Bianca Razor | Romania | + 1.73″ |
| 7 | Patience Okon | Nigeria | + 2.24″ |
| 8 | Ashley Kelly | British Virgin Islands | + 4.14″ |