Patrik Elias and Adam Henrique, who scored twice, also tallied in the opening period as the Devils beat the Flyers for the third time in three games this season. Andrei Loktionov had the prettiest goal for New Jersey, with a toe-drag move that left Flyers goalie Ilya Bryzgalov at his mercy.
Johan Hedberg had 23 saves for New Jersey, which has won two straight and three of four after a six-game losing streak.
Jakub Voracek and Scott Hartnell scored for the Flyers, who have lost four of five.
The Flyers were their own worst enemy, giving up two goals with bad pinches, another that went in off the skate of Matt Read, and another on a giveaway behind their net.
Philadelphia defenseman Andrej Meszaros got the Devils going, giving up the puck behind his net in the opening minutes. His pass up the middle of the ice was weak, and Steve Bernier got the puck. The rebound of his shot went to Henrique, who took a backhander that caromed to Elias for a tap-in goal.
Voracek tied it 1-1 on a power play by scoring his 13th goal. Wayne Simmonds set it up with a pass from beside the net to Voracek, who was alone in the left circle.
Henrique gave the Devils the lead for good 36 seconds later with a shot from the side boards that deflected past Bryzgalov off Read's skate.
Kovalchuk made it 3-1 late in the period when Read made a bad pinch on a power play. It led to a breakaway by Kovalchuk, who scored his 10th of the season and second short-handed against Bryzgalov. He also scored a short-handed goal on a penalty shot in the season opener.
Loktionov stretched the lead to 4-1 early in the second period, taking advantage of another bad pinch to lead a counter attack. He fooled Bryzgalov and scored his fourth goal.
Henrique made it 5-1, scoring on a power play for his ninth of the season.
Hartnell closed out the scoring late for the Flyers.
The Devils, who defeated the Flyers in five games in the second round of last season's playoffs, are 3-0 against Philadelphia this season - all in Newark. New Jersey has scored in the opening three minutes of each of those games.
Perhaps stirred by the loss, Philadelphia leaders Danny Briere and Claude Giroux feverishly worked on exercise bikes with their heads down.
NOTES: This was the first time the Devils scored four goals since a 5-3 win over the Flyers on Feb. 15. ... The teams will play in Philadelphia on Friday night, their next to last meeting of the season. ... Flyers D Luke Schenn was scratched because of the flu.