His many successes include winning the Nordic combined World Cup in 2002, 2003 and 2008.

He also has won three silvers at the Winter Olympics in the sprint (2002) and team (2002, 2006) events.

Ackermann is the first person to win the 15 km individual World Championships three straight times and the first to do it at the World Championships or Winter Olympic level since fellow (East) German Ulrich Wehling did it during the Winter Olympics of 1972, 1976, 1980.

Ackermann has also won the Nordic combined event at the Holmenkollen ski festival three times, with 2 wins in the individual competition (2002, 2004) and a win in the sprint competition (2003).

In 2003, Ackermann received the Holmenkollen medal (shared with Felix Gottwald).