Gagner, who was signed by the Jets late in the off season was expected to provide veteran savvy to the team's fourth line.
It paid dividends on this night as Gagner's first goal as a Winnipeg Jet started a three goal outburst in just over a four minute span.
Mark Scheifele scored twice for the Jets on the night.
Kyle Connor also scored for Winnipeg.
Nikolaj Ehlers had two assists.
Connor Hellebuyck made 40 saves for the Jets, who opened their regular season with a win.
Jaroslav Halak turned aside 30 shots for New York, who were playing their third game in four nights.
Artemi Panarin broke in alone on Hellebuyck after leaving the penalty box 9:09 into the game but was stymied by the Winnipeg goaltender who calmly made a blocker save.
Mark Scheifele opened the scoring just over a minute later when Nikolaj Ehlers beat Rangers forward Ryan Carpenter to a loose puck along the end boards before getting the disc to a wide open Kyle Connor who simply redirected it through his legs and right to Mark Scheifele who made no mistake, slinging a wrister past Halak, beating him low just inside the right post to make it 1-0 Jets at 10:29.
The goal was his first of the season.
There was no scoring in the second period.
Jordan Hunt scored just under four minutes into the third after Vincent Trocheck's centering pass went off of Jets defenceman () skate and right to Hunt who snapped a high shot off the center bar inside the Winnipeg goal to knot the contest at 1.
The goal was his 1st of the season.
Sam Gagner scored at 15:35 of the third after a goal mouth scramble, shovelling a loose puck sitting in the crease past Halak to give Winnipeg a 2-1 lead.
The goal was his first as a Jet.
Mark Scheifele scored at 18:23 of the 3rd, converting a Pierre-Luc Dubois feed past Halak to make it 3-1 Jets.
The goal was his second of the season.
Kyle Connor added an empty netter with 20 seconds left in the third to seal the win for the Jets.
Both teams return to action on Monday as New York hosts Anaheim while Winnipeg kicks off a three-game road trip against Dallas.
SHOTS-NEW YORK 41 WINNIPEG 34
ATTENDANCE-14,553
NOTES-The Rangers finished the game with 11 forwards afteer Ryan Carpenter left the game in the second period after being cut with a skate blade.
Jets Head Coach Rick Bowness tested postive for COVID and was not behind the bench. Associate Coach Scott Arniel took over. Bowness isn't expected back until next week.
