The United States won gold in six minutes 2.14 seconds and Romania took silver in 6:07.04. Canada was third in 6:09.34.
"We were a little bit behind at the start, but we trusted our rhythm just as we have been doing in practice," said Canadian coxswain Kristen Kit. "We rowed back into contention and the women responded to the calls. There were a lot of hearts beating together in this one boat."
Kit, from St. Catharines, Ont., was joined by Vancouver's Lisa Roman, Toronto's Jennifer Martins, Saskatoon's Carolyn Ganes, Susanne Grainger of London, Ont., Ottawa's Sarah Black, Victoria's Christine Roper, Natalie Mastracci of Thorold, Ont., and Cristy Nurse of Georgetown, Ont.
Black, Roper, Mastracci and Nurse also won a silver medal in the women's four on Friday.
"It's the first time I've doubled up at the worlds, so to be on the podium twice is pretty special," said Nurse. "For me, it was nice to have that extra event to keep us sharp and once you're on the podium you want to be back there."
Only Mastracci remains on the team from last year's Olympic silver-medal winning boat. The women's quadruple sculls picked up Canada's other medal with a silver on Saturday.
"Overall, the Canadian team competed here with a lot of determination and pride," said Rowing Canada high performance director Peter Cookson. "The women's team performed to world-class standards and it was a pleasure to watch them race here.
"The lightweight men made significant strides towards our goal of inching them back up to world standards. Our heavy men, while we are all disappointed with the results, are showing character and resolve that will certainly benefit them for next year and beyond."
Great Britain won gold in the men's eight, finishing ahead of Germany and the United States. Canada did not send a men's eight team to the world championships this year.
"We've got a lot of hard grinding to do over the fall, winter and spring, and I know all of the athletes on the team are itching to get back at it," Cookson said. "Our team motto is integrity, pride and performance. This team is starting to show those characteristics in many ways."
In other events on the last day of competition, Nils Jakob Hoff and Kjetil Borch of Norway won the men's double sculls. They took the lead at the midway point of the race and held off a late challenge from Rolandas Mascinskas and Saulius Ritter of Lithuania to claim their first world title.
The Lithuanians were second followed by Francesco Fossi and Romano Battisti of Italy.
Donata Vistartaite and Milda Valciukaite of Lithuania won the women's double sculls event, beating Fiona Bourke and Zoe Stevenson of New Zealand. Ekaterina Karsten and Yuliya Bichyk of Belarus were third.
Denmark won the men's lightweight double four, finishing ahead of New Zealand and Britain.
Ondrej Synek of the Czech Republic took the men's single sculls, finishing ahead of Angel Fournier Rodriguez of Cuba and Marcel Hacker of Germany. Australia's Kim Crow took top honours in the women's single sculls beating New Zealand's Emma Twigg and Mirka Knapkova of the Czech Republic.
With files from The Associated Press.