The 22-year-old De Grasse, seen as the sprinting heir to Usain Bolt when the great Jamaican calls it quits at the London world championships in August.
The 22-year-old De Grasse, seen as the sprinting heir to Usain Bolt when the great Jamaican calls it quits at the London world championships in August, would have been celebrating a personal best had the wind of +4.8sec not exceeded the permitted limit.
It was a third successive Diamond League win for De Grasse whose personal best remains the 9.91sec he ran to win bronze at last year's Rio Olympics.
Ivory Coast's Ben Youssef Meite was second on Sunday in 9.84sec with Ryan Shields of Jamaica in third on 9.89sec.
"It's great to sprint in such conditions, you cannot dream of any better," said the Canadian.
"Before I came here, I was told that it might be a bit cold but when I warmed up I realised that I could set a good time.
"I am very happy to have won despite the wind. I feel that I'm improving year after year. But these are only preparations for the big show of the worlds."
"That's the fastest I've ever run, it's going to be a shock to the body. Tomorrow's going to hurt a little bit, but I’m just looking forward to the next race and see what I can do legally."
Elsewhere, Timothy Cheruiyot of Kenya won the men’s 1500m in a world-leading time of 3min 30.77sec.
His compatriot and triple world champion Asbel Kiprop was fourth in 3:33.17 with Bahrain’s Alsadik Mikhou (3:31.49) and Ethiopia’s Aman Wote (3:31.63) filling the spaces in between.
"I am very happy," said Cheruiyot. "The race went to plan –- I tried to go at 300m. I’ll go back to Kenya now and prepare for the world championship trials. I will be really happy if I can make it to London. This was good preparation for this."
In the 110m hurdles, Olympic silver medallist Orlando Ortega of Spain edged 2015 world champion Sergei Shubenkov with a time of 13.09sec to 13.10sec.
Britain’s European indoor champion Andrew Pozzi and Antonio Alkana of South Africa were disqualified.
In the women's events, Ivory Coast’s Murielle Ahoure edged the 200m with a winning time of 22.68sec ahead of Canada’s Crystal Emmanuel and Rebekka Haase of Germany.
Burundi's Francine Niyonsaba, silver medallist in Rio, won the 800m making the most of the absence of two-time Olympic champion Caster Semenya who had won in Oslo on Friday.