The United States, which won the inaugural World Team Trophy in 2009, entered the final day leading in the overall standings and finished with 57 points. Canada was next with 51, two points ahead of Japan.
Tatiana Volosozhar and Maxim Trankov of Russia finished first in the pairs event with a score of 210.47. Duhamel, from Lively, Ont., and Radford, from Balmertown, Ont., were next with 191.15 points.
The Canadians, who won bronze at the world championship, used a routine that included triple throws and six level-four elements.
"There were some mistakes," Duhamel said. "But the way that we skated, the way we felt in the middle of the program, we were both very aware and relaxed at the same time.
“What we loved about the competition is that it really built that unit, that feeling of being a team.”
The Canadians used music from the "Angel" soundtrack for their routine. Cheng Peng and Hao Zhang of China were third with 174.40.
The team event will be included in the Olympic program for the first time in Sochi.
Akiko Suzuki of Japan won the women’s event ahead of Americans Ashley Wagner and Gracie Gold. Canadian champion Kaetlyn Osmond of Marystown, N.L., was seventh and Gabrielle Daleman of Newmarket, Ont., was 11th.
"I didn’t know what to expect coming here," said Osmond. "It was a lot of fun and the team provided great support which made it so enjoyable and lifted the pressure. This whole season has been a dream come true for me."
It was Daleman's senior international debut.
"I was honoured to compete here," added Daleman. "Even though I didn’t have a best skate, I was feeling nervous and the support of my teammates really helped me."
Wagner was fourth after the short program. She received 188.60 points for her routine to Samson and Delilah to finish second. Gold was third with 188.03 points. Suzuki won with 199.58 points.
"I could not be prouder of the U.S. team," Wagner said. "Every member contributed to this victory and I am proud to be the captain."
Suzuki turned in an elegant performance that included seven triple jumps.
"I gave it all I had and am relieved it's over," Suzuki said. "It's been a very difficult season. It wasn't the cleanest routine I've skated but I'm happy with finishing first."
Wagner hit all her jumps in a lively routine. Her only blemish was when she took off with the wrong edge of her skate on a triple lutz.
"I really made sure to capture the character of Delilah," Wagner said. "The personality of the program is what carried me to such a strong performance. Competing has been fun for me this season, and more than anything else that is what made a difference this year."
Gold, who was third after the short program, also completed all her jumps in a routine to Life is Beautiful.
Mao Asada of Japan finished a disappointing fifth after being downgraded on her trademark triple axel at the start of her program. Russia's Adelina Sotnikova, who was first after the short program, was sixth.
The World Team Trophy brings together selected skaters from the six countries that scored the highest combined points at major senior and junior competitions.
A team event will be included for the first time at the Winter Olympics next year in Sochi, although the format will differ slightly from the World Team Trophy.
With files from The Associated Press.