| POS | Rank | Heat | BIB | ATHLETE | COUNTRY | RESULTS | ms* | 
|---|---|---|---|---|---|---|---|
| 1 | 1 | 2 | 1757 | Antti SAINIO | 
 FIN                 | 
                49.36 Q WU20L | .351 | 
| 2 | 2 | 2 | 1681 | Michal RADA | 
 CZE                 | 
                49.36 Q WU20L | .352 | 
| 3 | 3 | 2 | 2340 | Vance NILSSON | 
 USA                 | 
                49.82 q | |
| 4 | 1 | 1 | 2190 | Njabulo MBATHA | 
 RSA                 | 
                49.90 Q | |
| 5 | 2 | 1 | 1790 | Sam LUNT | 
 GBR                 | 
                50.00 Q NU20R | |
| 6 | 4 | 2 | 1709 | Joaquin ALONSO | 
 ESP                 | 
                50.22 q NU20R | |
| 7 | 3 | 1 | 1971 | Kyo KIKUTA | 
 JPN                 | 
                51.04 | |
| 8 | 1 | 3 | 1966 | Daniel WRIGHT | 
 JAM                 | 
                51.11 Q | |
| 9 | 2 | 3 | 1626 | Ramón FUENZALIDA | 
 CHI                 | 
                51.33 Q PB | |
| 10 | 4 | 1 | 2222 | Akalanka KUDA LIYANAGE | 
 SRI                 | 
                51.45 | |
| 11 | 5 | 2 | 1901 | Fintan DEWHIRST | 
 IRL                 | 
                51.65 | |
| 12 | 3 | 3 | 1967 | Kairi GONDA | 
 JPN                 | 
                51.80 | |
| 13 | 6 | 2 | 1900 | David DAVITT | 
 IRL                 | 
                51.93 | |
| 14 | 7 | 2 | 2014 | Ali Abdulfattah ALRUMAYH | 
 KSA                 | 
                52.25 PB | |
| 15 | 5 | 1 | 2214 | Mitja ZUBIN | 
 SLO                 | 
                52.55 | |
| 16 | 4 | 3 | 2059 | Jose Eduardo AGUADO | 
 MEX                 | 
                52.57 | |
| 17 | 5 | 3 | 1584 | Lucas DE ALMEIDA | 
 BRA                 | 
                52.67 PB | |
| 18 | 6 | 3 | 2360 | Premier WYNN | 
 USA                 | 
                52.76 | |
| 19 | 7 | 3 | 2283 | Cheyne WEST | 
 TTO                 | 
                53.09 | |
| 20 | 6 | 1 | 1914 | Paolo BOLOGNESI | 
 ITA                 | 
                53.92 | |
| 21 | 8 | 2 | 1963 | Trevoy SMITH | 
 JAM                 | 
                54.24 | |
| 22 | 7 | 1 | 2065 | Maximiliano NUÑEZ | 
 MEX                 | 
                57.96 | |
| 23 | 8 | 3 | 1637 | Jingwei GUO | 
 CHN                 | 
                1:03.89 | |
| 1 | 1698 | Joel VON DE AHÉ | 
 DEN                 | 
                DNS | 
ms - Milliseconds - shown when two or more competitors finish with the same time down to hundredths of a second