Both sides will rue not finding the net in the tight Eastern Conference playoff race.
Despite suspension robbing the Union of standout Amobi Okugo at the heart of its back line, the Zolos managed to limit service to Marco Di Vaio, who recorded a hat trick in their last meeting.
The Italy veteran wasn't entirely toothless, though. A poacher's shot under pressure following a Zac MacMath spill in the first half went just wide of the post, and he had a goal called back for offside in the second period.
The night was equally fruitless for Jack McInerney, as the youngster made his 10th consecutive appearance without a goal before he was subbed in the 80th minute.
Montreal, by not taking all three points, exposes itself to challenges from New York and Kansas City for its top spot. Philadelphia is unlikely to drop out of the playoff spots this weekend, but a failure to win gives the teams behind it with games in hand an opportunity to narrow the gap.