Halak made 21 saves for his third shutout this season. He has won seven straight, allowing only eight goals. The Islanders have won four in a row and nine of 10.
''It's a different makeup, it's a different attitude, a little different swagger to our team,'' coach Jack Capuano said. ''No matter what the score is or what the adversity that we're facing throughout a game or how the momentum is going, we're just going to continue to play the way we know how.''
Mason made 43 saves through regulation and was heavily tested in the final few minutes. He reached up to glove Okposo's rising drive with 1:40 left in the third period and fell onto his back in the crease.
''The boys played well,'' Tavares said. ''You want to score, and if you don't beat the goaltender he was probably better than you in the play. You just stay with it. What else can you do? You look to the next shift. You can't control what is in the past.''
Philadelphia managed only 20 shots in regulation. The Flyers had a great chance to break the deadlock when New York's Matt Martin charged Luke Schenn from behind and slammed him into the boards. But the power play was shortened after 49 seconds when Wayne Simmonds was called for high-sticking.
The Islanders had the better of the chances in the first two periods. New York held a 12-6 shots edge through the opening 20 minutes and 27-16 before the third, not counting several drives that were wide of the mark or deflected out of play.
''We want to and have to play better,'' Simmonds said. ''We were trying to pass too much. They are a fast team, and they showed that all night. Mase was awesome, for sure. He kept us in it all night.''
The only thing that found its way into the net before the shootout was Islanders defenseman Johnny Boychuk, who got shoved in there by Flyers defenseman Braydon Coburn with 7:55 left in the second.
Boychuk nearly broke the scoreless tie 46 seconds into the second when he fired a drive from the right point that found its way through traffic and was barely stopped by Mason's skate at the post.
Mason also stood tall when Brock Nelson used speed to get free to the net. Mason blocked his shot from in close that appeared to catch a piece of the post, too.
Halak faced fewer shots, but also was challenged. He denied Pierre-Edouard Bellemare in tight in the second period, but Halak's best stop came in the first when he held his ground through several dekes as Sean Couturier came in on a short-handed breakaway.
''We just have to keep playing the same way,'' Halak said. ''We will enjoy this win tonight and get back to work.''
NOTES: A moment of silence was held for Pat Quinn, a former coach of the Flyers and several other teams. Quinn died on Sunday. ... Islanders D Matt Donovan made his season debut, and was joined by Brian Strait, who was scratched nine of the previous 10 games. They replaced Thomas Hickey, who sat out for the first time this season, and fellow defenseman Calvin de Haan, who was scratched after playing 17 straight games. Both defensemen were sidelined by illness.