Duhamel, from Lively, Ont., and Radford, from Balmertown, Ont., had 72.70 points. Yuko Kavaguti and Alexander Smirnov of Russia were second with 64.60 points and world junior champions Xiaoyu Yu and Yang Jin of China were third with 60.15.
''The way we skated today is how we skate every day in practice,'' said Radford. ''This is how we aim to skate at every competition. It feels amazing to skate like that and we're really looking forward to carrying the momentum into the long program.''
Olympic champion Yuzuru Hanyu fell twice in his short program and finished fifth in his comeback from injuries after a collision in warmups at the Cup of China.
Before Friday's short program, Hanyu conceded that he wasn't in top condition and it was evident early when he fell on his opening quad toeloop. He hit his next jump — a triple axel — but fell again on a triple lutz-triple toeloop to finish with 78.01 points.
Takahito Mura of Japan finished first with 86.28 points, ahead of Jeremy Abbott of the United States, who earned 81.51. Daisuke Murakami of Japan was third with 79.68 points.
Elladj Balde of Montreal was seventh and Jeremy Ten of Vancouver was eighth.
Hanyu was diagnosed with bruising to his head and chin after colliding with Chinese skater Yan Han in warmups at the Cup of China three weeks ago. He wasn't sure until Wednesday if he would take part in the NHK Trophy but decided to participate because he felt good during practice.
"I feel like I've recovered enough and just tried to skate as normal," Hanyu said. "Obviously this is disappointing. But the free skate is one I'm confident with and I will do my best tomorrow."
Hanyu is bidding for one of three available spots for the Grand Prix Final next month in Barcelona.
"Right now, I'm not thinking about the final, I just want to go out and have a successful NHK," Hanyu said.
Mura, skating to "Carmen," opened with a quad toeloop-triple toeloop and hit all his other jumps to record a season-best score.
Abbott, who is also bidding for a spot in the GP Final, didn't have a quad jump in his program but skated a clean routine that included a triple flip-triple toeloop, a triple lutz and a triple axel.
"I'm very pleased," Abbott said. "I love this program."
Gracie Gold of the United States took the lead after the women's short program, boosting her chances of qualifying for the Grand Prix Final.
Skating to "Adagio," the U.S. champion hit all her jumps to score 68.16 points and finish ahead of Alena Leonova of Russia, who had 68.11. Kanako Murakami of Japan was third with 64.38 points.
Gabrielle Daleman of Newmarket, Ont., was seventh.
"I skated a really nice short program," Gold said. "I'm happy because I made a lot mistakes at Skate America. I had solid jumps and spins today and want the same consistency tomorrow."
Gold is vying for one of two open spots for next month's GP Final in Barcelona. She earned a bronze medal at Skate America last month.
"I think there are positives and negatives in qualifying for the GP Final," Gold said. "When you consider the U.S. Nationals are in January, it kind of interrupts your schedule for that but of course it means you have done very well."
With files from The Canadian Press.