Heats
samedi 11 août 2018, 03h00 GMT – 03h00 GMT
| Nom | Équipe | Temps | |
|---|---|---|---|
| 1 |  Caeleb Dressel | United States | 51.69″ |
| 2 |  Jack Conger | United States | + 0.07″ |
| 3 |  Vinicius Lanza | Brazil | + 0.29″ |
| 4 | Michael Andrew | United States | + 0.3″ |
| 4 | Grant Irvine | Australia | + 0.3″ |
| 6 | Yuki Kobori | Japan | + 0.54″ |
| 7 | Iago Amaral | Brazil | + 0.58″ |
| 8 | Zach Harting | United States | + 0.77″ |
| 9 |  David Morgan | Australia | + 0.78″ |
| 10 | Yuya Yajima | Japan | + 1.17″ |
| 11 | Josiah Binnema | Canada | + 1.35″ |
| 12 | William Pisani | Canada | + 1.44″ |
| 13 | Leonardo de Deus | Brazil | + 1.45″ |
| 14 | Jiahao Shen | China | + 1.47″ |
| 15 | Mack Darragh | Canada | + 1.49″ |
| 16 |  Shinri Shioura | Japan | + 1.64″ |
| 17 | Nao Horomura | Japan | + 1.79″ |
| 18 | Owen Daly | Canada | + 2.22″ |
| 19 | Shuchang Zhou | China | + 2.43″ |
| 20 | Jarod Hatch | Philippines | + 3.06″ |
| 21 |  Ruslan Gaziev | Canada | + 3.28″ |
| 22 | Timothy Yen | Philippines | + 4.71″ |
| 23 | Rafael Barreto | Philippines | + 5.01″ |
| 24 | Armand Pierre Chan | Philippines | + 8.39″ |
| 25 | Noel Keane | Palau | + 10.74″ |
| 26 | Nelson Batallones | Northern Mariana Islands | + 17.26″ |
| 27 | Mark Imazu | Guam | + 17.53″ |