It ruined what would have been an historic celebration in his hometown, but it paved the way for one of the most dramatic comebacks in NASCAR racing when Ambrose re-grouped with a wounded car to re-start the race way back in 28th place with 25 laps to go.
He diced and sliced his way through the field, finally making it back to second place, this time behind Alex Tagliani's No. 12 Penske Racing Dodge.
He finally got past Tagliani and never looked back until he took the checkered flag.
Ambrose had started the race from the back after an adventure in itself getting to Montreal from Michigan International Speedway, where he had Sprint Cup practice in the morning for Sunday's Pure Michigan 400.
"We got a helicopter ride to the airport, flew to Montreal in a plane, got through customs, got in another helicopter and then got in a boat to get us to the track," Ambrose said.
But it was all worth it when he ended one of the most frustrating string of losses in his career.
"Every year we have come here we feel we have he best car," he said. "We have finished second twice and other two times we made mistakes or were taken out of races we should have won.
"It sure is nice to finally get one in the win column."
Ambrose admitted that those four previous failures flashed though his mind when he saw Villeneuve came across Turn 1 on Lap 44.
"We had the two best cars and we both wanted the lead," he said of his fight with Villeneuve. "It was unlucky for Jacques that the crash took away his chance to win, but it was lucky that it didn't do that for us."
Tagliani, meanwhile, had a front-row seat of the show as he was behind both Villeneuve and Ambrose on that turn.
"I thought when I saw Jacques dive into the corner that he was going to take us out too," Tagliani said. "We were just able to avoid the chaos."
It was the second Nationwide race in a row that Villeneuve managed to create mayhem on the track. In June at Road America he took out potential leaders Max Papis and Brian Scott in a very risky pass late in the race.
This latest incident could just end any chance the former F1 world champion and Indianapolis 500 winner has of re-inventing myself as a driver in a top NASCAR series.
When it was all said and done, however, Ambrose refused to say anything bad about Villeneuve.
"I have no hard feelings," he said in the post-race celebration. "You know when you race Jacques that he is a 100% kind of guy."
In another bit of drama Saturday, Patrick Carpentier waved goodbye to a 20-year-racing career.
The end came 10 laps sooner than he would have liked after his No. 99 Pastrana Waltrip Racing Toyota expired from damage done earlier in the race when he was sideswiped by the No. 66 Toyota of Steve Wallace.
Carpentier was not happy and one of his crew grabbed Wallace after the race to make the point.
"I hate to leave the sport like this," Carpentier said. "I guess Steve Wallace hasn't learned how to brake yet."
On the good news side of the ledger, J.R. Fitzpatrick battled through several issues, including an electrical failure, to come back with a fifth-place finish -- the best of his Nationwide career -- in the No. 67 Go Canada Racing Ford Mustang.
Ron Fellows, who led late in the race in the No. 5 JR Motorsports Chevrolet, ran short on fuel and settled for a 11th-place finish.
Top 10 results of NASCAR Nationwide NAPA 200 at Curcuit Gilles VIlleneuve:
1: Marcos Ambrose Ford
2: Alex Tagliani Dodge
3: Michael McDowell Toyota
4: Steve Wallace Toyota
5: J. R. Fitzpatrick Ford
6: Scott Speed Chevrolet
7: Carl Edwards Ford74
8: Justin Allgaier Chevrolet
9: Jason Leffler Chevrolet
10: Elliott Sadler Chevrolet