Just 55 seconds after Jeff Tambellini's late second-period goal drew the Islanders even at 2, Langkow put the Flames back in front with 3:02 left in the period.
On the winner, Rene Bourque weaved his way down the ice before spotting Langkow breaking to the goal on the opposite side. Bourque slid a pass through the slot, and Langkow buried a shot inside the goal post behind Joey MacDonald.
Langkow has six goals and six assists during a seven-game points streak.
Bourque, Mike Cammalleri, Curtis Glencross, and Adam Pardy also scored for Calgary in the Northwest Division-leading Flames' sixth consecutive home victory.
In his 12th straight start, Miikka Kiprusoff made 24 saves to win his NHL-best 25th game (25-11-3).
Trevor Smith added his first NHL goal for New York, 0-13-1 in its last 14 road games.
Calgary put it away on Pardy's first NHL goal at 7:25 of the third. The 6-foot-4 defenseman pinched in from the blue line and one-timed Jarome Iginla's centering pass into a vacant net with MacDonald caught down on the ice.
Swedish junior star Mikael Backlund made his NHL debut for the Flames. In just over 10 minutes of ice time, Backlund had a shot on goal.
Notes: Radek Martinek (shoulder) was back in the Islanders' lineup after missing 17 games. ... Backlund wore No. 60, the first time anyone has worn that number for the Flames in a regular-season game.