Before turning to competitive cycling Nils Andersson won a district championship in a team cross-country skiing race in 1931. The following year Andersson won his first of 10 team championships with Hammarby IF, with his last victory coming in 1944. In 1943 he finished second in the Mälaren Runt, a cycling race around lake Mälaren, considered to be the most important Swedish road race at the time. In 1936 Andersson was selected to compete in the road race at the Berlin Olympics but he did not start the event. He also worked as a bicycle dealer in Stockholm.