The Devils grabbed a two-goal lead in the opening 20 minutes and spent the rest of regulation trying to protect it. When Ottawa tied it late, there were no signs New Jersey would get back on top of the Senators again.
Langenbrunner changed that 1:55 into the second overtime when Travis Zajac sent him off on a breakaway, and the veteran forward shoved the puck past goalie Ray Emery to lift New Jersey to a 3-2 victory Saturday night.
That gave the Devils a home split of the first two games in the Eastern Conference semifinal series.
Langenbrunner got the puck in the neutral zone, fought off a hook from trailing defenceman Joe Corvo and shoved the puck past sprawled goalie Ray Emery. The puck slipped between Emery's pads as Corvo crashed into the net, knocking it off its moorings as Langenbrunner celebrated.
"It was a great play by Travis to get the puck up," Langenbrunner said. "It kind of bounced off something and found its way to my stick. I was just fortunate to find the net.
"The best thing was I didn't have enough time to think about it."
Martin Brodeur, who gave up all of Ottawa's five goals in the opener, kept the Devils in this one. He ended up with 43 saves to earn his 94th post-season victory, second only to Patrick Roy (151).
"We don't worry about Marty," Langenbrunner said. "Just when he seems to have his worst game, you know he will come up with one of his best."
Devils captain Patrik Elias returned from a one-game absence because of the flu to help set up Brian Gionta's early goal and send the Devils on their way to a tie in the best-of-seven series. It now shifts to Ottawa for Game 3 on Monday and Game 4 on Wednesday.
New Jersey seemed set to win it in regulation, after first-period goals by Gionta and Sergei Brylin, but Dany Heatley tied it for the Senators with 26.4 seconds left in the third.
Only once have the Devils won a series they trailed 2-0.
"If those guys won, it would have been devastating for us," Brodeur said.
The Devils controlled the first period after falling behind 4-0 in the opening 20 minutes of Game 1, but the Senators took over - outshooting the Devils 39-15 between the second period and the start of the second overtime.
New Jersey kept Ottawa on its heels by converting 2-of-5 power-play chances in the first period.
"That takes everyone kind of out of the game. It puts a lot of pressure on our goaltender and penalty killers," said forward Jason Spezza, who assisted on both Senators goals. "We're a pretty good 5-on-5 team but when we're killing penalties the whole game it's pretty tough to beat anyone."
Daniel Alfredsson started Ottawa's comeback with a power-play goal 4:23 into the second period.
As Elias watched from bed and fought a fever, Brodeur gave up all five goals Thursday in the 5-4 loss. But in his NHL-record 150th consecutive playoff start, Brodeur held off the charging Senators in the second and third periods when they held a 26-8 shots advantage.
Ottawa tied it when Spezza passed the puck out from behind the net in front to Heatley, who fired the puck past defenceman Paul Martin in the crease and by Brodeur in the closing seconds with Emery on the bench for an extra attacker.
"It was a tough situation for us to let go a lead like that late in the third," Brodeur said. "We came through again."
Until then, Brodeur made the most of a new set of equipment. He ditched the old gear after the rough Game 1 outing.
"Everything worked out well, the pads, the glove, the blocker. I felt I wanted to change," Brodeur said. "Sometimes with new equipment, you feel a little bigger in there. I felt good."
Emery made 30 saves, 14 in the first period when the Devils broke through.
Elias, the Devils' career leader in playoff points with 102, made the final dish on a four-man passing play to set up Gionta's seventh goal of these playoffs at 1:43, tying teammate Zach Parise for the NHL lead and giving New Jersey its first lead of the series.
It was the Devils' first power-play goal in four chances in the series. New Jersey enjoyed a stellar first period, outshooting the Senators 16-5. Quite a difference from Game 1.
It was such a good period this time, New Jersey savoured every second. While on a long 5-on-3 power play, Brylin stretched the lead to 2-0.
Brylin squared off in the left circle with Spezza and won a faceoff. With players jostling, the puck jolted forward and ticked off Brylin's skate. Brylin lunged toward the loose puck and let it fly as he fell, sending a shot over Emery's glove as the horn and green light signalled the end of the period.
Officials went to the phone as a video review ensued. It was clear that the puck entered the net with 0.2 seconds remaining, much to the dismay of Spezza, who complained as both teams left the ice for intermission.
Alfredsson cut Ottawa's deficit to 2-1 on Ottawa's third power play. Heatley moved the puck behind the net to Spezza, who passed it to Alfredsson by the boards. The Senators captain brought it into the left circle and let go a quick drive that beat Brodeur for his fourth goal of the playoffs.
The Senators finished the period with a 14-4 shots advantage and repeated that effort in the third with a 12-4 edge.
Notes: Ottawa has never led 2-0 in a series. The Senators have won Game 1 eight times in 16 matchups, including in this year's first round against Pittsburgh. ... The game drew 19,040 fans, the Devils' first sellout of the season. ... Each team had two power-play chances in the first overtime.