Erik Haula scored twice, and Patrice Bergeron had a goal and two assists for the Bruins (32-17-4), who have won the first three of a six-game road trip that continues at the Anaheim Ducks on Tuesday.
"We got a few breaks early on to get the lead on the road," Boston coach Bruce Cassidy said. "We were pretty good at playing the right way, and now they're chasing the game. I don't know if they're built to chase a lot of games from behind. That's always an advantage, and then we started clicking a little bit. We were due for one of these nights where pucks go in the net."
Jonathan Quick allowed five goals on 19 shots before being pulled in the second period for the Kings (29-18-7), who had won five in a row. Cal Petersen made 11 saves in relief.
"We're upset," Los Angeles forward Alex Iafallo said. "That's a loss that we don't want, to lose that big, obviously. We're going to have to look at ourselves in the mirror and learn from our mistakes, but it was a good run."
DeBrusk scored at 1:01 of the first period when his wrist shot from the right face-off circle trickled past Quick to give the Bruins a 1-0 lead. DeBrusk then made it 2-0 at 13:27 when he intercepted Kings defenseman Mikey Anderson's clearing attempt and scored from the slot.
He completed the hat trick 53 seconds into the second period on a redirection of Bergeron's shot from the right boards to give Boston a 3-0 lead.
"As soon as you get two, you always want the third, and I was lucky enough to get it and help the team, put us up by three against a defensive team like L.A.," DeBrusk said.
Bergeron made it 4-0 at 11:40, redirecting David Pastrnak's slap shot from the left point six seconds into a power play, and Taylor Hall made it 5-0 at 12:42 off the rush.
