They clinched the final post-season berth in the Eastern Conference with a dramatic 3-2 shootout win over the New Jersey Devils today at East Rutherford.
The victory - in which they wasted a two-goal lead and gave up the tying goal with less than a second left in regulation - eliminates the Toronto Maple Leafs.
Wade Dubielewicz stopped the last two penalty shots for the Islanders, who finish with 92 points, one more than Toronto.
New York looked to have the game in hand after a pair of Richard Park goals put them up 2-0.
But John Madden scored twice in the final five minutes to set up the dramatic finish.