Florida obtained Wisniewski Tuesday in a trade with the New York Islanders and he paid instant dividends. Michael Cammalleri fired a shot that Tomas Vokoun turned aside but Wisniewski scored on the rebound with 1:19 to go in the extra period.
Wisniewski scored on the power play midway through the second period after Florida had taken a 2-0 lead. Brian Gionta tied it with 7:06 left in the middle stanza, also scoring on the power play.
Montreal completed a seven-game road trip, its longest of the season, and turned in a 2-5 record on the journey. Alex Auld got the win with 20 saves.
Vokoun stopped 45 shots for Florida, which has lost three out of four.