Semifinal 1
mercredi 8 août 2018, 19h35 GMT – 19h35 GMT
| Nom | Équipe | Temps | |
|---|---|---|---|
| 1 |  Matthew Hudson-Smith | Great Britain | 44.76″ |
| 2 |  Jonathan Borlee | Belgium | + 0.11″ |
| 3 | Ricardo Dos Santos | Portugal | + 0.38″ |
| 4 |  Matteo Galvan | Italy | + 0.41″ |
| 5 | Dwayne Cowan | Great Britain | + 0.69″ |
| 6 | Lucas Búa | Spain | + 0.72″ |
| 7 |  Pavel Maslak | Czech Republic | + 0.83″ |
| 8 |  Lukasz Krawczuk | Poland | + 1.02″ |