After two seasons in the European Cup, Björnlund made his debut in the Freestyle Skiing World Cup on January 15, 2005 and reached 23rd place in Lake Placid . Twelve days later, he made it into the top ten for the first time. In the 2005/06 season he achieved two top 10 placements in the World Cup, but his best result was fifth at the 2006 Winter Olympics . In the three following winters Björnlund could only show good results sporadically, but stood out at the 2009 World Cup in Inawashiro with a sixth place in the dual moguls competition.
Largely unexpectedly, Björnlund won his first World Cup race on December 11, 2009 in Suomu and confirmed this result with another victory the following day. In the 2009/10 season he stayed in the top ten with one exception and finished eighth at the 2010 Winter Olympics .