Bråthen began his international career at the 1986 World Junior Championships in Lake Placid , where he won the bronze medal on the large hill. Previously, the Norwegian junior champion had already become in the same year. On December 30, 1987, he made his debut in the Ski Jumping World Cup as part of the opening competition for the Four Hills Tournament 1987/88 and reached 70th place in Oberstdorf . In 1988 he was again Norwegian junior champion. At the end of the 1987/88 season he was able to jump into the top ten for the first time in Meldal and came in 9th place. In the first competition of the following season in Sapporo , he made it onto the podium for the first and only time in his career. After further good performances, he ended the 1988/89 season in 27th place in the overall World Cup ranking. At the Nordic World Ski Championships in Lahti in 1989 , he won the silver medal in team competition. In jumping from the normal hill he jumped to 15th and from the large hill to 11th place. From 1992 Bråthen moved to the Ski Jumping Continental Cup after his performance in the World Cup decreased. In 1994 he won the gold medal on the normal hill at the Norwegian Championships in Vegårshei . Two years later he won the gold medal again with the team, but shortly afterwards ended his active ski jumping career.
Bråthen has been a member of the Norwegian Ski Association since 2001 and is head of the ski jumping department there. Bråthen is one of the supporters of international women's ski jumping.