400m Boys Heats, Heat:1 of 4 ; Official result since 19:29
First + 4 fastest to Final
| Rank | Lane | ID | Name | PB | Team | Cat | Result | Info | Video |
| 1 | 6 | 206 | Sribu Aekalak | 50.12 | Bangkok | 51.93 | Q | ||
| 2 | 8 | 153 | Talalas Nedas | 52.56 | Kaunas | 52.17 | q | ||
| 3 | 2 | 113 | Jezek David | 51.11 | Brno | 52.71 | B | ||
| 4 | 7 | 165 | Turcu Ovidiu Alexandru | 55.41 | Medias | 57.17 | |||
| 5 | 5 | 173 | Gomilar Domen | 56.6 | Gorje | 1:11.46 | |||
| 6 | 4 | 163 | Todoran Ianis | 59.23 | Medias | 1:11.84 | |||
| 3 | 167 | Islamov Danis | Ufa | DNS |