Berger joined the national biathlon team in 2001. During the 2004 Biathlon World Championships in Oberhof, Germany, he won silver medals in the 15 km mass start and the 4 x 7.5 km relay. Berger also won two gold medals in the military world championships that same year (cross country and patrol). Berger finished fifth in the 2004 overall World Cup, and won several gold medals from the Norwegian Biathlon Championships. At the 2007 Biathlon World Championships in Rasen-Antholz, Italy, Berger was part of the Norwegian team that won silver in the 4 x 7.5 km relay.
Berger has also been competing in cross country since 2002. He also won the 30 km and relay at the 2003 Norwegian Cross-country Championships in Molde. Berger won a gold in the 4 x 10 km at the 2005 FIS Nordic World Ski Championships in Oberstdorf and finished 4th in the 15 km in those same championships. Berger won the gold medal in the at 15 km at the 2007 FIS Nordic World Ski Championships in Sapporo in 2007, in a race were changing weather conditions gave him a massive advantage over his strongest competitors[1]. He is the first person to win medals at the World Championships in biathlon and Nordic skiing in the same year.
