Heats
vendredi 10 août 2018, 03h00 GMT – 03h00 GMT
| Nom | Équipe | Temps | |
|---|---|---|---|
| 1 |  Zach Apple | United States | 48.03″ |
| 2 | Caeleb Dressel | United States | + 0.1″ |
| 3 | Blake Pieroni | United States | + 0.18″ |
| 4 |  Kyle Chalmers | Australia | + 0.2″ |
| 5 |  Pedro Spajari | Brazil | + 0.35″ |
| 6 |  Jack Cartwright | Australia | + 0.4″ |
| 7 | Marcelo Chierighini | Brazil | + 0.41″ |
| 8 | Nathan Adrian | United States | + 0.44″ |
| 9 |  Katsumi Nakamura | Japan | + 0.53″ |
| 10 | Shinri Shioura | Japan | + 0.65″ |
| 11 | Townley Haas | United States | + 0.66″ |
| 12 | Gabriel Santos | Brazil | + 0.69″ |
| 13 | Alexander Graham | Australia | + 0.72″ |
| 14 | James Roberts | Australia | + 0.8″ |
| 15 | Andrew Seliskar | United States | + 0.96″ |
| 15 | Katsuhiro Matsumoto | Japan | + 0.96″ |
| 17 | Clyde Lewis | Australia | + 1.05″ |
| 18 |  Yuri Kisil | Canada | + 1.13″ |
| 19 | Marco Antonio Ferreira Junior | Brazil | + 1.2″ |
| 20 | Juran Mizohata | Japan | + 1.48″ |
| 21 | Javier Acevedo | Canada | + 1.67″ |
| 22 | Daniel Hunter | New Zealand | + 1.83″ |
| 23 | Ruslan Gaziev | Canada | + 1.84″ |
| 24 | Reo Sakata | Japan | + 1.88″ |
| 25 | William Pisani | Canada | + 2.02″ |
| 26 | Owen Daly | Canada | + 2.08″ |
| 27 | Yuki Kobori | Japan | + 2.09″ |
| 28 | Ippei Watanabe | Japan | + 2.15″ |
| 29 | Elijah Winnington | Australia | + 2.41″ |
| 30 | Grant Irvine | Australia | + 2.53″ |
| 31 | Shaofeng Liu | China | + 2.66″ |
| 32 | Rafael Barreto | Philippines | + 5.07″ |
| 33 | Issa Al-Adawi | Oman | + 5.22″ |
| 34 | Noel Keane | Palau | + 7.91″ |
| 35 | Armand Pierre Chan | Philippines | + 8.02″ |
| 36 | Lennosuke Suzuki | Northern Mariana Islands | + 9.7″ |
| 37 | Mark Imazu | Guam | + 12.27″ |
| Federico Grabich | Argentina | DNS |