Thomas Hickey's one-timer off a feed from Brock Nelson at the 12:31 mark of overtime lifted the Islanders to a dramatic 4-3 victory in Game 3 of their best-of-seven series against the Panthers.
"We had a good shift and grinding them out a little bit," Hickey told the AP. "Somebody went to change, I saw a gap and an unbelievable pass and it just got off my stick."
Frans Nielsen, Ryan Pulock and Shane Price also scored for the Isles in their postseason debut at Barclays Center. Kyle Okposo and John Tavares registered two assists each.
Thomas Greiss had 36 saves in the New York victory.
Game 4 is Wednesday (8 p.m., USA) back at Barclays.