The 30-year-old has signed a deal with Swedish club Skelleftea AIK for the 2020-21 season, Sportsnet's Chris Johnston reports.
The homecoming ends a six-year stint with the San Jose Sharks in which Karlsson suited up for 396 games, posting 60 goals and 112 points over that span. He played all 24 games of the Sharks' 2016 Stanley Cup Final run, posting eight points in just under 14 minutes of average ice-time as San Jose was ultimately felled by the Pittsburgh Penguins.
Karlsson's best NHL campaign came in his first go-round in the league, 2014-15, wherein the Lycksele, Sweden native put up 13 goals and 24 points in 53 games.
Signed to a three-year, $6-million deal with San Jose back in 2017, Karlsson played out the final season of the pact in 2019-20.