Ott buried the rebound of a Jordan Leopold shot on the game-winner and salvaged a victory for the Sabres after they had blown a 2-0 third-period lead.
Tyler Ennis also found the net and Jhonas Enroth notched 32 saves as the struggling Sabres recorded only their second win in eight contests.
Max Pacioretty and Colby Armstrong each tallied late in the game to forge a tie and earn a standings point for the Northeast Division-leading Habs.
Carey Price turned aside 18 shots for Montreal.
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