Brock Nelson and Anthony Beauvillier scored for New York, which has lost four in a row (0-2-2) and is 5-8-4 this season despite playing 12 of its first 17 games at home. Halak made 32 saves in his seventh straight start.
"At the end of the day, the guys are coming in and they're working hard," Islanders coach Jack Capuano said. "You can't beat them down. You've got to stay with it, you've got to show them confidence, and eventually you hope this will turn for the guys."
WATCH: All Penguins vs. Islanders highlights
Crosby gave the Penguins a 1-0 lead with a power-play goal 15:19 into the game. Halak made an initial save on Letang's slap shot from the right point, but he lost sight of the rebound, and Crosby easily converted from the top of the right circle for his 11th of the season.
Pittsburgh outshot New York 16-5 in the first period.
"I thought it was a pretty solid effort," Penguins coach Mike Sullivan said. "I really liked our first period; a lot of energy, we were playing the game the right way. We put pucks on the net. We could have had a few more goals there in the first period. They pushed back, but I really liked the response in the third period."
Nelson tied it 1-1 with a power-play goal at 1:51 of the second period. John Tavares rushed the puck up ice and passed to Ryan Strome at the right faceoff circle. Strome played the puck into the slot for Nelson, who beat Murray with a wrist shot.