The victory allowed Dallas to move within a point of the Phoenix Coyotes for the Western Conference's final playoff spot.
The Stars have 79 points. Phoenix received a point for an overtime loss against the Rangers to reach 80.
Winnipeg continued to fade out of the postseason race. The Jets are 2-6-3 in their past 11 games. One of the victories was a 7-2 rout of visiting Dallas eight days earlier.
Stars goalie Kari Lehtonen made 32 saves.
Jamie Benn had two assists for Dallas, which was 2 for 4 on the power play.
Bryan Little scored for the Jets with 2:44 remaining.
Whitney scored from the left faceoff circle on a slap shot that went off Al Montoya and into the upper left corner. Montoya finished with 25 saves.
Late in the period, Dallas' Valeri Nichushkin beat two defenders for a breakaway on the power play, but Montoya stopped the rookie's backhand shot.
Winnipeg's best chances came midway through the first, but Lehtonen stopped Blake Wheeler in close and saved Jim Slater's wraparound attempt.
The Stars finished the period with a 12-11 edge in shots, and a 1-0 lead.
Just 13 seconds into Dallas' third power play, Seguin pulled the puck out of a pile in front and lifted a shot over Montoya at 16:09 of the second.
Seguin's 32nd goal was his sixth in five games against Winnipeg this season. His 10 points against the Jets are his highest total against any opponent.
Winnipeg nearly scored on its first power play of the game. With two minutes remaining in the second, Lehtonen reached back to smother the puck after a shot from the blue line bounced off the crossbar.
Defense dominated in a period when the Stars outshot the Jets 9-7.
Winnipeg spent much of the third period in the Dallas end, peppering Lehtonen with 15 shots, but fell a goal short.
NOTES: Jets captain Andrew Ladd missed the game because his wife, Brandi, gave birth to a baby girl Sunday. He is expected to rejoin the team Thursday at San Jose for the second game of a five-game trip. Evander Kane joined Little and Michael Frolik on the first line. ... Goalie Ondrej Pavelec missed his fifth consecutive game because of an upper body injury. Wheeler left the ice in the third period after skating into an open door by the Dallas bench. ... Sergei Gonchar's first-period assist was his eighth in the past six games against the Jets.