Boldsen had his debut on the Danish national handball team on August 23, 1998, and in the following ten years he played 186 matches for the team, scoring 405 goals. On September 30, 2008, he announced that he was resigning from the national team due to the increased traveling hours following his change to FC Barcelona. In his career, he was part of winning the 2008 European Championship, and part of the bronze winning team in the 2007 World Championship as well as bronze in the European Championships in 2002, 2004, and 2006. Boldsen played at the 2008 Summer Olympics in Beijing, where Denmark reached the quarter finals, and placed seventh after being eliminated by Croatia.