Adam Lowry and Kyle Connor also scored for the Jets (23-13-3), who had dropped three of four. Andrew Copp and Nikolaj Ehlers each had two assists, and Connor Hellebuyck made 20 saves.
Ottawa lost for the third time in four games. Ryan Dzingel had a goal and an assist for the Senators (13-22-4), and Josh Norris scored a power-play goal in the third period. Anton Forsberg made 42 saves.
Dzingel said his team wasn't ready to play ''and clearly that showed.''
''I'm sure we're going to fix it and be ready to go next game,'' he said. ''Because that clearly wasn't good enough.''
Ottawa pulled within one on Connor Brown's 10th goal with 3:09 left, but Winnipeg held on. Brown has scored in four straight games.
The Jets improved to 5-1-0 against the Senators this season.
''I've got way, way more respect for Ottawa than I think most people do. And I think that might be why we're 5-1 on them,'' Jets coach Paul Maurice said.
Dubois opened the scoring 2:10 into the game, flicking a quick shot into the top-left corner of the net. Lowry made it 2-0 with his eighth of the season 4:19 into the second.
Dubois said he's still developing chemistry with new linemates Blake Wheeler and Paul Stastny.
''(Wheeler's) a great passer so he makes it easy out there sometimes,'' he said. ''He sees the ice so well that I just have to get to the open space and more often than not, it's on my blade.''
Dzingel got Ottawa on the board 29 seconds after Lowry's goal. Winnipeg lost track of the puck behind the net and Dzingel picked it up, popping it over Hellebuyck's pad.
But the Jets opened a 4-1 lead with two more in the second. Dubois scored a power-play goal at 8:38, and Connor added his 18th at 16:12.
Ottawa was 1 for 4 on the power play, and Winnipeg went 1 of 3. The Senators have power-play goals in their last three games.
''I was all right with our game straight through. And I didn't feel that we were under siege,'' Maurice said. ''They're going to push, pull their goalie, those types of things. I really liked our offensive game, the way we tried to shoot the puck.''
Senators: Host the Edmonton Oilers on Wednesday.
Jets: Visit the Montreal Canadiens on Thursday.
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