| POS | Rank | Heat | ATHLETE | COUNTRY | RESULTS |
|---|---|---|---|---|---|
| 1 | 1 | 1 | Germany U20 |
GER |
43.80 Q WU20L |
| 2 | 1 | 2 | Ireland U20 |
IRL |
44.27 Q |
| 3 | 2 | 2 | Italy U20 |
ITA |
44.52 Q |
| 4 | 3 | 2 | France U20 |
FRA |
44.80 Q SB |
| 5 | 2 | 1 | Great Britain & NI U20 |
GBR |
44.84 Q |
| 6 | 3 | 1 | Switzerland U20 |
SUI |
45.01 Q SB |
| 7 | 4 | 2 | Poland U20 |
POL |
45.19 q |
| 8 | 4 | 1 | Australia U20 |
AUS |
45.26 q SB |
| 9 | 5 | 2 | Brazil U20 |
BRA |
45.28 SB |
| 10 | 5 | 1 | Canada U20 |
CAN |
45.68 SB |
| 11 | 6 | 2 | Austria U20 |
AUT |
45.99 |
| 1 | PR of China U20 |
CHN |
DQ | ||
| 2 | Jamaica U20 |
JAM |
DQ | ||
| 1 | United States U20 |
USA |
DQ |