Karlsson spent the past two seasons with Northeastern University, where he had 34 points (15 goals) in 49 games.
The 6-foot-3, 200-pound native of Stockholm, Sweden, was limited to 17 games last season due to a wrist injury that required season-ending surgery. He had five goals and three assists as a sophomore.
During his freshman season, Karlsson led the Huskies in scoring (a first by a freshman since the 2006-07 season), when he had 10 goals and 16 assists in 32 games. He tied for the team lead in goals and finished 12th nationally among first-year skaters in points per game (0.81) and third in Hockey East.
Prior to enrolling at Northeastern, Karlsson played two seasons (2009-11) with the Green Bay Gamblers of the United States Hockey League. During his first season with the Gamblers, he had 30 points (eight goals) and helped Green Bay win the Clark Cup. In 2010-11, he had 40 points (16 goals) and helped Green Bay back to the Clark Cup Final.