 He played for Brynäs through 2004–05, before moving to Almtuna IS in 2005–06, before settling down to one team Bofors IK for the 2006–07 season.Karlsson was tied for the team lead in scoring with 32 points (11 goals) in 2006-07 and added 34 penalty minutes in 44 games.Karlsson signed with the Ottawa Senators in 2007 and played two games with the Senators' AHL team, the Binghamton Senators, before returning to Sweden to play with Färjestads BK on assignment from Ottawa on October 26, 2007.