| | Event type
400 metres, Boys
| Date | 11 – 14 October 2018 | |
|---|---|---|
| Status | YOG | |
| Location | Athletics Field, Parque Olímpico de la Juventud, Villa Soldati, Buenos Aires | |
| Participants | 26 from 26 countries | |
| Format | Two stages with final results determined by cumulative time. | |
| Pos | Competitor | NOC | Time | |||
|---|---|---|---|---|---|---|
| 1 | Luis Avilés |  MEX | 1:34.23 | Gold | ||
| 2 | Kennedy Luchembe |  ZAM | 1:34.34 | Silver | ||
| 3 | Nicholas Ramey |  USA | 1:34.87 | Bronze | ||
| 4 | İlyas Çanakçı |  TUR | 1:35.78 | |||
| 5 | Lorenzo Benati |  ITA | 1:36.58 | |||
| 6 | Bernat Erta |  ESP | 1:37.31 | |||
| 7 | Dilan Bogoda |  SRI | 1:37.33 | |||
| 8 | Solomon Diafo |  GHA | 1:37.55 | |||
| 9 | Keegan Bell |  AUS | 1:38.63 | |||
| 10 | Yefim Tarasov |  KAZ | 1:38.81 | |||
| 11 | Douglas Mendes |  BRA | 1:39.04 | |||
| 12 | Junior Rouse |  SKN | 1:40.70 | |||
| 13 | Raymond Oriakhi |  BAH | 1:41.02 | |||
| 14 | Bernard Olesitse |  BOT | 1:41.08 | |||
| 15 | Wang Yu-Hsuan |  TPE | 1:41.36 | |||
| 16 | Gnanzou Desire Kodjo |  CIV | 1:41.58 | |||
| 17 | Evaldo Whitehorne |  JAM | 1:42.48 | |||
| 18 | Potchara Petchkaew |  THA | 1:43.00 | |||
| 19 | Christel Rakotomalala |  MAD | 1:47.19 | |||
| Yusuf Anan |  BRN | – | ||||
| Dalitso Gunde |  MAW | – | ||||
| Ludovic Oucéni |  FRA | – | ||||
| Malik John |  IVB | – | ||||
| Jared Sylvester |  GRN | – | ||||
| Clevonte Lodge-Bean |  BER | – | ||||
| Berat Mustafa |  MKD | – |