Brock Nelson and Simon Holmstrom scored, and Ilya Sorokin made 30 saves for New York (5-4-3), which has lost three straight (0-2-1).
“I thought we did a lot of good things tonight,” said Islanders forward Bo Horvat, who played after missing one game with a lower-body injury. “Obviously, we lost the special teams game. Obviously, that killed us. … We have to figure out ways to bear down and score those big goals in those big times because obviously these games are important. These points are important.”
Frederic gave the Bruins a 1-0 lead at 14:05 of the first period from the high slot. Coyle worked the puck to van Riemsdyk behind the goal line, and he set up Frederic for a wrist shot.
Nelson tied it 1-1 on the power play at 17:23, poking in the puck on a rebound from Noah Dobson’s point shot.
Coyle’s power-play goal gave Boston a 2-1 lead at 6:06 of the second period. His one-timer in front of the net beat Sorokin after combining with Pastrnak and Pavel Zacha.
Holmstrom tied it 2-2 with a short-handed goal at 2:50 of the third period off a Marchand turnover at the Islanders blue line, but Pastrnak put Boston ahead 3-2 just 43 seconds later at 3:33 with a power-play goal from the left circle.
“We score a huge short-handed goal, and then we’ve got to find a way to kill the penalty, and we didn’t,” Islanders coach Lane Lambert said. “Right now, we’ve got to find a way to dig ourselves back in and dig ourselves out a little bit. There’s too many times that [in] these costly moments, we’re not up to the task at the moment."