His greatest successes in biathlon were the 2002 Olympic victory in the relay, the 1998 Olympic silver medal over 10 km and the bronze medal in the 10 km sprint at the 2006 Winter Olympics in Turin. Andresen also often had to overcome crises: In 1998, after a dispute, he was not placed in the silver relay of Nagano (he was replaced by Dag Bjørndalen ). In 2000 he won the Sprint World Championship gold in Oslo ; However, the racing jury found that he had already inserted a magazine into the gun before the start , which for safety reasons is only allowed at the shooting range immediately before shooting. Despite opposing protests, the jury made the controversial decision that Andresen was allowed to keep his title. Although he later voluntarily returned his gold medal, the result officially remained unchanged.
Andresen has also been taking part in the cross-country skiing world cup since 1998, and in 2009 he became Norwegian champion on the 50 km freestyle course.