Phil Housley and Paul McDermid scored first-period goals and goaltender Bob Essensa stopped 36 shots, leading Winnipeg.
The loss was just the second in 10 games for Toronto.
Housley opened the scoring at 6:41 and MacDermid netted the winner at 11:59 as the Jets dominated the opening period.
Guy Larose, with his fifth goal in three games, beat Essensa in the second period but that was all Toronto could muster.
Pat Elnyuik clinched the win at 13:14 of the third period.
Toronto goalie Rick Wamsley, who got the start because Grant Fuhr is out with an injured right knee, was sharp in the opening minutes.
But Wamsley was beaten cleanly on Housley`s slap shot from the left circle. The speedy defenseman was in full flight when he ripped a shot that was buried in the Leaf net before Wamsley could close his pads.
MacDermid used a bit of fancy footwork to score the winner. The veteran knocked the puck down with his right foot much as a soccer player would stop a ball. The puck dropped on to MacDermid`s stick and he banged a shot from the lip of the crease at 11:59.
