Comeau opened the scoring on the power play midway through the first period and tipped in a shot 41 seconds into the middle stanza.
Kyle Okposo and Andrew MacDonald scored for the Islanders, who ended a four-game losing streak in the opener of a five-game homestand.
Montoya stopped 33-of-34 shots, finally giving up a goal to John Madden with 8:27 to play in the third.
Niklas Backstrom gave up three goals on 19 shots before being removed for Jose Theodore in the second period.
Minnesota began the night in 10th place in the Western Conference, where at the start of play Wednesday the fifth through 12th-place teams were separated by just four points.