As soon as he got the ice for his first shift, Hartnell found an unattended puck in front of the Jets' net and immediately slapped it past Ondrej Pavelec to put the Flyers up, 1-0.
"I just shot it as hard as I could," Hartnell said. "I'll take it. It's nice on your first shift, right in the slot there's a little present waiting for you there."
Mason turned away 25 shots in the matinee that began at 11:30 a.m., including an impressive pad save on Matt Halischuk on a 2-on-1 chance in the second period. He improved to 3-0-1 in his career against the Jets (12-12-4).
The Flyers (11-12-2) won their fifth straight game at home after dropping their previous two on the road at Florida and Tampa Bay.
"It's huge," Mason said. "Our Florida effort was terrible. Both games were lackluster, so to come home and get a big win before we go on the road for  days is a step in the right direction."
Both Flyers goals came off Winnipeg turnovers.
Hartnell's score was the Flyers' lone goal in a dominating opening period in which they outshot the Jets 13-2.
"Morning game, obviously the first period was one where we weren't engaged in the game," Winnipeg coach Claude Noel said. "You don't know what to expect. ... Obviously it wasn't a great situation."
Sean Couturier had a short-handed breakaway opportunity in the first period that Pavelec stopped with a right pad save. But in the second he once again forced a Jets turnover on the penalty kill, this time beating Pavelec on a breakaway for his second goal of the year.
Couturier also played a big role on the Flyers' penalty kill that held the Jets without a goal in six power-play opportunities.
"I was really impressed with [Couturier's] effort," Mason said. "He stepped up his game."
Michael Frolik finally put the Jets on the scoreboard with 7:07 left in the third when he slipped one by Mason in front of a crowded net.
Peppered with 34 shots, Pavelec made 32 saves but fell to 7-4-1 lifetime against the Flyers.
The Flyers, who entered with a power-play goal in eight consecutive games, also failed to score on four tries. They opened the second period with 1:25 of 5-on-3 time but couldn't manage a shot while up two men. Philadelphia has yet to score a 5-on-3 goal this season.
"The 5-on-3 wasn't good," coach Craig Berube said. "Got to execute better and come up together. You can't be dumping [the puck] in on a 5-on-3. You got to do a better job. They know that."
The loss snapped Winnipeg's five-game winning streak against Eastern Conference teams and was just its second defeat in Philadelphia in eight games.
"We just weren't very good," Noel said. "Was that an early morning game? I don't know. That would be a poor excuse, because they're ready to play."
The win was an important one for the Flyers, who are 7-2-1 in their past 10 games but begin a six-game road trip Saturday night in Nashville.
"Flying up to Canada, down south in Texas, we're gonna have to get our rest and do the right things," Hartnell said. "We've played solid on the road except for our last two games, and we've got to continue that and make this the best road trip of the year."
- Flyers captain Claude Giroux's points streak ended at six games.
- Friday's meeting was the second of two between the teams this season. The Jets won in a shootout in Winnipeg 3-2 on Nov. 15.
- The Jets' six-game road swing continues against the New York Rangers on Monday.