Lehtonen, who turns 29 in November, was 32-22-4 with a.922 save percentage and four shutouts last season. He had a 2.33 goals against average over 59 games.
The new deal pays him $5.9 million a season through 2017-18.
"Kari Lehtonen has worked extremely hard in his time with the Dallas Stars to establish himself as an elite goaltender in the NHL," said Stars General Manager Joe Nieuwendyk. "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."
Atlanta took Lehtonen with the second selection overall in the 2002 NHL draft. Lehtonen went to Dallas in a traded in February 2010.
He is 134-111-28 over 285 NHL games with a goals against average of 2.79.