Tomas Vincour tied the game late in the third 3 win over the San Jose Sharks.
Jamie Benn posted a goal and an assist and Michael Ryder also scored for the Stars, who have won four straight and sit atop the Pacific Division with 79 points. Lehtonen made 45 stops and turned aside all five skaters in the shootout.
San Jose sits in the eighth spot in the Western Conference, one point ahead of Los Angeles and Colorado.
The game was tied going into the third after Mitchell fought off a defender and was able to get a backhand past Lehtonen with just 1.2 seconds left in the second.
The Sharks then took the lead just 25 seconds into the third when Marleau's wrist shot from inside the right circle beat Lehtonen.
Dallas, however, was able to tie the game six minutes later after Benn punched the puck in off a broken play in front.
San Jose regained a 3-2 edge with 3:32 to play after Pavelski was able to put in a rebound in front off a shot from Dan Boyle at the right of the net.
The Stars pulled Lehtonen for the extra attacker late and were rewarded as Vincour was able to get the puck in during a scrum in front just before Niemi was able to get a glove on it with 1:15 to play in regulation.
After a scoreless first period, the Stars took a 1-0 lead when Ryder split the defense up the middle and chipped the puck into the net for his 29th of the year.
Ryder's career-high in goals was 30 in the 2005-06 and 2006-07 seasons when he was in Montreal...Dallas hosts Anaheim on Saturday...Dallas continues its four-game road trip in Phoenix on Saturday...San Jose had won all three games against Dallas this season and five straight coming into Thursday's contest.