Mike Ribeiro had a goal and an assist while Trevor Daley, Jamie Benn and Tom Wandell each scored for the Stars, who have won three of their last four.
Jose Theodore gave up four goals on 31 shots for the Wild, who have lost three of their past four games.
Benn scored his 19th goal of the season with 7:58 left in the first period and Lehtonen stopped four shots to help the Stars take a 1-0 lead into the second period.
In a span of 1:31 in the later stages of the second, the Stars took control of the game.
The first came with 4:08 to play as a pass by Daley at the left side of the net hit off the stick of a Wild defender and went in.
Just over a minute later, the Stars made it a 3-0 game as Wandell’s snap-shot from the right circle beat Theodore low for his sixth goal of the season.
A mere 18 seconds later, Dallas took a 4-0 lead off a miscue from Minnesota as a defender blindly threw the puck out front from behind the net and Ribeiro one-timed home the gift.
Lehtonen stopped seven shots in the second and needed to make just three in the third for the whitewash.
Lehtonen has 15 shutouts in his career…Dallas has taken all three games against Minnesota and six straight. These two will play each other on the final day of the regular season in Saint Paul…Dallas hosts Los Angeles on Sunday…Minnesota plays at Vancouver on Monday.