He has participated in FIS competitions since 2000 . At the Junior World Championships in 2000 in Štrbské Pleso, Slovakia, 57th over 10 kilometers and 26th over 30 kilometers. A year later he achieved better results in the junior championships in Karpacz, Poland, with tenth place over 10 kilometers and 22nd place over 30 kilometers. At his last Junior World Championships in 2002 in Schonach in the Black Forest , he achieved his best placement in the junior division over 30 kilometers in eighth place. His best result in a World Cup race he achieved with third place in a relay race in La Clusaz, France in the 2006/07 season . His best individual result was a twelfth place over the 15 kilometers in Lahti in the same season. In Alpencup he took five wins. He also came in second four times and third three times. His best overall placement was fifth in the 2008/09 season . At German championships he won in 2008 with the relay, in 2009 over 10 km freestyle and with the relay and in 2010 over 10 km classic, in the pursuit and in the team sprint together with Andy Kühne .
Seifert completed his last official race on March 9, 2014. He lives in Oberwiesenthal .