Heats
jeudi 9 août 2018, 03h00 GMT – 03h00 GMT
| Nom | Équipe | Temps | |
|---|---|---|---|
| 1 |  Katie Ledecky | United States | 1′ 55.16″ |
| 2 | Allison Schmitt | United States | + 1.2″ |
| 3 |  Leah Smith | United States | + 1.65″ |
| 4 |  Taylor Ruck | Canada | + 1.68″ |
| 5 | Katie McLaughlin | United States | + 1.72″ |
| 6 | Kayla Sanchez | Canada | + 2.23″ |
| 7 |  Rikako Ikee | Japan | + 2.27″ |
| 8 | Mallory Comerford | United States | + 2.32″ |
| 9 | Gabrielle Deloof | United States | + 2.7″ |
| 10 | Mikkayla Sheridan | Australia | + 2.89″ |
| 11 | Katie Drabot | United States | + 2.93″ |
| 12 | Rebecca Smith | Canada | + 3.32″ |
| 13 | Chihiro Igarashi | Japan | + 3.35″ |
| 14 | Madeline Groves | Australia | + 3.64″ |
| 15 | Tomomi Aoki | Japan | + 3.67″ |
| 16 | Rio Shirai | Japan | + 3.72″ |
| 17 |  Brianna Throssell | Australia | + 3.95″ |
| 18 | Abbey Weitzeil | United States | + 4.14″ |
| 19 | Kyla Leibel | Canada | + 5.07″ |
| 20 | Kennedy Goss | Canada | + 5.29″ |
| 21 | Waka Kobori | Japan | + 5.92″ |
| 22 |  Larissa Oliveira | Brazil | + 7.05″ |
| 23 | Nicole Oliva | Philippines | + 7.68″ |
| 24 | McKenna DeBever | Peru | + 7.91″ |
| 25 | Yui Yamane | Japan | + 7.95″ |
| 26 | Sayaka Akase | Japan | + 8.08″ |
| 27 | Rosalee Santa Ana | Philippines | + 12.41″ |
| 28 | Miranda Cristina Renner | Philippines | + 23.34″ |
| 29 | Gianna Vivien Garcia | Philippines | + 24.43″ |
| 30 | Mineri Gomez | Guam | + 30.62″ |
| 31 | Osisang Chilton | Palau | + 32.03″ |