The world bronze medallists received 146.22 points for their routine performed to a medley of rock band Muse, giving them a winning total of 220.72.
Ksenia Stolbova and Fedor Klimov of Russia were second with 213.72, followed by China's Wenjing Sui and Cong Han with 194.31.
"Our goal coming here was to stand on the podium, so to win is a bonus," said Duhamel.
Duhamel, from Lively, Ont., and Radford, from Balmertown, Ont., are enjoying a standout season, with victories in both their Grand Prix events — Skate Canada International and NHK Trophy in Japan.
Weaver, Poje take ice dance
Canadians came out on top in the ice dance competition as well.
Kaitlyn Weaver and Andrew Poje won the ice dance with a total of 181.14 after earning 109.80 for their free dance to Vivaldi's "Four Seasons."
"Andrew and I felt like we gave everything," Weaver said. "We felt calm and prepared and that's the best zone to compete in. It's been our best competition yet."
Americans Madison Chock and Evan Bates remained in second with 167.09, while France's Gabriella Papadakis and Guillaume Cizeron moved up into third with 162.39.
Russians own women's competition
In the women's competition, Elizaveta Tuktamysheva of Russia won the Grand Prix Final after extending her lead with a personal best free skate on Saturday.
The 17-year-old, who broke her foot in March, cruised through her program to finish with 136.06 points for a winning total of 203.58.
"When I was injured I understood I could not give up skating," Tuktamysheva said through a translator. "I have this fighting spirit."
Fifteen-year-old countrywoman Elena Radionova finished second with 198.74.
American Ashley Wagner rebounded from her shaky short program with a score of 129.26— 0.26 from her personal best free skate — to repeat her third-place finish from last year's final with 189.50 points.