Duclair put the Islanders up 1-0 with a power-play goal at 10:43 of the first period. Duclair took a wrist shot from the top of the right circle, beating Georgiev on the glove side.
Pageau gave the Islanders a 2-0 lead at 19:22 after Noah Dobson fed him a pass at the left dot for a one-timer on the short side.
"I thought we had some really good chances," Pageau said. [The power play] is going to be key for our push to the end of the season."
San Jose outshot New York 20-8 in the first period.
At 6:26 of the second period, Kovalenko deflected Shakir Mukhamadullin's shot from the point to make it 2-1 on the power play.
"I think we did a pretty good job getting in front of [Sorokin, getting] tips," Celebrini said. "I mean, we score a goal like that. For sure, we can do it more, and it's only going to create more traffic for him."