Kopitar faked a backhand shot, put the puck on his forehand and beat a prone Martin Brodeur.
Los Angeles has won all nine of its road games in the playoffs, an NHL record. The Kings are now one win shy of the NHL record for postseason road victories.
More importantly, they are three wins away from the franchise’s first NHL title. They have won 11 consecutive road playoff games dating back to last season.
Colin Fraser scored in the first period for the Kings, the No. 8 seed in the Western Conference who beat the top three teams to get to their first Stanley Cup Finals
Anton Volchenkov tied it late in the second period for New Jersey, the East’s sixth seed.
Kopitar took a pass by Justin Williams from along the left wing boards and skated in alone on Brodeur. As soon as he rifled the puck into the net, he raised his hands and banged himself into the boards, facing the crowd off to Brodeur’s right.
The veteran goaltender dejectedly skated off to the locker room as the rest of the Kings piled on Kopitar.
Kings goaltender Jonathan Quick finished with 17 saves in what was a relatively easy night.
Brodeur had 23 saves as the Devils lost in overtime for just the second time this postseason; they have won four times. Los Angeles is 3-0 in overtime this spring.
The Devils had two great chances to take the lead early in the third period, and for a split second it appeared they went ahead with 16:02 to play in regulation when Zach Parise scored off a wild goal-mouth scramble.
While the horns went off and the fans celebrated, referee Dan O’Halloran quickly waved off the goal.
It was reviewed in Toronto and replay clearly showed Parise swept the puck into the net with his hand.
Defenseman Mark Fayne missed a wide-open net six minutes later from the edge of the crease in what was the Devils’ best period of the night.
Los Angeles had chances to extend its lead, but Brodeur, who was the difference in the Devils’ victory over the rival Rangers in the conference finals, made three good saves.
The best stop by the 40-year-old, three-time Cup winner came on the opening shift of the second period when he blocked Kopitar point blank on the edge of the crease.