The 28-year-old, an Olympic silver medallist in Sochi, switched allegiance from the US to Britain in December and was taking part in his first halfpipe World Cup in over two years.
But he showed no sign of rustiness as he posted a score of 93.20 for his first World Cup win in four years as he also became the first British man to win halfpipe gold.
And after edging out hometown favourite Brendan Mackay and USA's Birk Irving to take the top step, Kenworthy admitted it felt good to be back doing what he loves best.
GB's Atkin, 18, continues fine form with World Cup silver
"I feel great," Kenworthy said. "It's my first halfpipe World Cup in two years, and it's my first competing under the British flag, and I'm just so, so happy.
"I landed a run that I'm happy with, the level of riding tonight was amazing, and I'm very happy to share the podium with Brendan (Mackay) and Birk (Irving).
"I didn't want to come back to competition slow and just kind of half-ass it. I wanted to come back really aggressive and strong, so it feels good.
"I honestly didn't know if I was coming back or if I was done competing, but I took some time off and really missed it. It's great to be back."
China's teenage sensation Eileen Gu produced three near-flawless runs to claim her first halfpipe World Cup win as Russian Valeriya Demidova secured the crystal globe.
Gu showed maturity beyond her age of 16 to earn a score of 94.00 and clinch the gold medal in Calgary, finishing ahead of Canada's Rachael Karker (89.20) and Demidova (87.20).
That finish for Demidova capped off a dream 2019/20 season for the 19-year-old, who took podiums in four of five competitions to earn the first-ever Freeski crystal globe for a Russian athlete.
Demidova took the overall top prize ahead of Karker and Zhang Kexin but it was Gu's night as she strengthened her case to be considered among the world's best free skiers.
"I don't think you can ever just expect to win a World Cup," she said.
"It's all about going in and doing the best you can, and I was able to perform and do something that I haven't been able to do before.
"I just did the best that I could do and this is the best that I could have hoped for."
Atkin continues fine form with World Cup silver
Smith and Howden claim ski cross crystal globes