Lehtonen, 28, was acquired by the Stars a few weeks before the trade deadline in February 2010 as the club's eventual replacement for longtime netminder Marty Turco.
Lehtonen was 32-22-4 last season with a .922 save percentage and a 2.33 goals-against average. He had four shutouts in 59 games.
In his time with Dallas, Lehtonen has set or tied career highs in games played (69), wins (34), save percentage (.922), goals-against average (2.33) and minutes played (4,119).
"Kari Lehtonen has worked extremely hard in his time with the Dallas Stars to establish himself as an elite goaltender in the NHL,"
general manager Joe Nieuwendyk said. "We believe that his best days as a goaltender are ahead, and that his work ethic and leadership will help guide this team into a perennial Stanley Cup contender."