The Jamaican got off to a blistering start with English Gardner before pulling away from her rival in the last 40 metres to win by 14 hundredths of a seconds.
American Gardner was second in 10.85 with the fast-finishing Michelle-Lee Ahye of Trinidad and Tobago third in 10.98, both also aided by an illegal wind of +2.4 metres per seconds.
Thompson, who last summer logged 21.66 -- the fifth fastest 200m of all time -- to take silver at the Beijing world championships, told Reuters things were coming together nicely for what she hoped would be a twin sprint assault in Rio.
"It's a stepping stone, so I'm taking it one step at a time. Each race that I run I'll see what I can correct with my coach and see what I have to do next," Thompson said. "I've been training really hard this year so I just went out there to execute and that's what I did and I came out victorious."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Thompson, third in the 60m at the world indoors in March, would have become the second fastest Jamaican woman behind reigning Olympic and world champion Shelly-Ann Fraser-Pryce (10.70) had it not been for the wind.
"My start isn't the best, but I’m working on it and I’ve been getting better," the 23-year-old said.
There was also local success in the men's blue riband sprint when Kemar Bailey-Cole, who withdrew from last year's world championships with a hamstring injury, recovered from a poor start to edge American Mike Rodgers by two hundredths of a second in 10.01.
His compatriot Julian Forte, who faded in the last 20 metres, was third in 10.06, while American former world champion Tyson Gay finished fifth in 10.08.
The wind also robbed American Brianna Rollins, the 2013 world champion, of the year's second fastest time in the 100m hurdles, as her 12.52 was aided by a trailing wind of +2.9 m/s.
World 400m silver medallist Shaunae Miller of the Bahamas ran a world leading 22.14 in the 200m but again the mark will not stand because of the +2.5 m/s wind.
(Editing by Nick Mulvenney)
