The six-foot-four, 205-pound native of Ludvika, Sweden, recorded three goals and six assists with 12 penalty minutes in 53 games this season. He was held pointless in six playoff games.
Lightning general manager Jay Feaster said he likes Karlsson's versatility.
"Karlsson is a very good skater who can play centre and is an effective face-off man and a good penalty killer," Feaster said Wednesday in a release. "In short, you can play him anywhere from your second through fourth lines as he is responsible defensively as well."
Originally drafted 148th overall by Calgary at the 1993 NHL draft, Karlsson was traded to Atlanta in 1999 and appeared in 153 games with the Thrashers from 1999 to 2002.
In 206 NHL regular-season games, Karlsson has recorded 14 goals and 33 assists.
Karlsson also spent several seasons playing in his homeland, leading the Swedish Elite League in points (55) in 2005-06. He also helped Sweden win a gold medal at the 2006 IIHF World Hockey Championship.