Heats
dimanche 12 août 2018, 03h00 GMT – 03h00 GMT
| Nom | Équipe | Temps | |
|---|---|---|---|
| 1 |  Michael Andrew | United States | 21.83″ |
| 2 | Caeleb Dressel | United States | + 0.34″ |
| 3 |  Katsumi Nakamura | Japan | + 0.38″ |
| 4 |  Yuri Kisil | Canada | + 0.45″ |
| 5 | Shinri Shioura | Japan | + 0.47″ |
| 6 |  Pedro Spajari | Brazil | + 0.49″ |
| 7 | Marcelo Chierighini | Brazil | + 0.51″ |
| 8 |  Gabriel Santos | Brazil | + 0.66″ |
| 9 | Daniel Hunter | New Zealand | + 0.68″ |
| 10 | Zach Apple | United States | + 0.68″ |
| 11 | Blake Pieroni | United States | + 0.7″ |
| 12 | Syunishi Nakao | Japan | + 0.71″ |
| 13 |  James Roberts | Australia | + 0.73″ |
| 14 | William Pisani | Canada | + 0.75″ |
| 15 | Jack Cartwright | Australia | + 0.77″ |
| 16 | Owen Daly | Canada | + 0.9″ |
| 17 | Katsuhiro Matsumoto | Japan | + 1.14″ |
| 18 | Ruslan Gaziev | Canada | + 1.14″ |
| 19 | Alexander Graham | Australia | + 1.23″ |
| 20 | David Morgan | Australia | + 1.24″ |
| 21 | Reo Sakata | Japan | + 1.31″ |
| 22 | Marco Antonio Ferreira Junior | Brazil | + 1.33″ |
| 23 | Elijah Winnington | Australia | + 1.45″ |
| 24 | Shaofeng Liu | China | + 1.52″ |
| 25 | Jarod Hatch | Philippines | + 2.14″ |
| 26 | Nao Horomura | Japan | + 2.33″ |
| 27 | Rafael Barreto | Philippines | + 2.69″ |
| 28 | Issa Al-Adawi | Oman | + 2.75″ |
| 29 | Timothy Yen | Philippines | + 3.18″ |
| 30 | Armand Pierre Chan | Philippines | + 3.52″ |
| 31 | Noel Keane | Palau | + 3.63″ |
| 32 | Lennosuke Suzuki | Northern Mariana Islands | + 4.75″ |
| 33 | Mark Imazu | Guam | + 6.16″ |
| 34 | Nelson Batallones | Northern Mariana Islands | + 7.91″ |
| Nathan Adrian | United States | DNS | |
| Federico Grabich | Argentina | DNS | |
| Grant Irvine | Australia | DNS |