Tomas Hertl scored a hat trick, and Kaapo Kahkonen made 35 saves for the Sharks (7-17-2), who have won two of their past three on a current six-game road trip after losing their first 10 games away from home this season.
“We’re happy about this group because we’ve gone through a lot of stuff this year," Hertl said. "This [win] shows me something. We could do it. Last game, we almost came back and against a really good team (6-5 loss at the New York Rangers on Sunday). We actually finished today, so feeling really good.”
Mike Reilly had a goal and an assist, and Simon Holmstrom and Bo Horvat each had two assists for the Islanders (10-7-7), who had won two in a row. Sorokin made 32 saves.
“It’s unacceptable. That’s all that needs to be said,” New York forward Brock Nelson said. “Up two at home, four or five minutes left, we should be putting two points in the bank and moving on. ... For whatever reason this is costing us too many times.”
It was the third time in four games that the Islanders blew a third-period lead. They allowed three goals in the third in a 5-4 loss to the New Jersey Devils on Nov. 28, and gave up the tying goal with three seconds left in regulation before rallying for a 5-4 overtime win against the Carolina Hurricanes on Nov. 30.
On the season, New York has been outscored 34-17 in the third period.
"I don't have any words for you on that," Islanders captain Anders Lee said. "It's just bad. It's really bad."
Kevin Labanc scored his first of the season on a redirection to get the Sharks to within 4-2 at 11:55 of the third.
“That second goal really gave us a ray of hope,” San Jose coach David Quinn said. “Really good job by that line, the (Nico) Sturm, Labanc, (Justin) Bailey line, establishing the forecheck, getting the puck up top, and (Nikita) Okhotiuk bombs it, and we get screens.”
Hertl cut it to 4-3 at 16:49 with Kahkonen on the bench for an extra skater. Granlund's shot from the point deflected off a couple of players to Hertl, who scored over Sorokin's left pad at the right post.
Hertl then scored another goal with Kahkonen on the bench to tie it 4-4 at 18:30, tapping in a backdoor pass from Eklund at the right post.