He led for all but one of the six rounds but it went to the wire, with four athletes still in contention with one to go, and he needed a tough final dive to win with a total of 505.20.
Dumais finished on 498.40 after a superb final effort that moved him into second above Canada's former champion Alexandre Despatie, who took his second bronze of the week after coming third in the synchronised three-metre with compatriot Reuben Ross.
China's Zhang Xinhua, who took silver in the one-metre springboard behind compatriot Qin Kai last week, came fourth.
The victory may help tone down the Chinese media's talk of a 'crisis' in their diving team after they missed out on three of the seven gold medals contested here before Thursday's final. China won all but one of the eight golds up for grabs at the Beijing Olympics last year.
Meanwhile, American Francis Crippen will keep his men's 10km open water bronze medal after winning an appeal against disqualification for not entering the final straight through the gate, a US team spokeswoman said on Thursday.
Italy tried to get the bronze awarded to Valerio Cleri, who finished fourth in Wednesday's race won by Germany's Thomas Lurz, with Crippen's compatriot Andrew Gemmell taking silver.
Meanwhile, the preliminary session of the women's 3M syncronised diving came to an end with the Chinese pair of Guo Jingjing and Wu Minxia in the lead with 342.90 points
