She dominated the distance and finished in the time 21.15 - 17 hundredths ahead of Australian star Emma McKeon who finished second.
Swedish Louise Hansson and Michelle Coleman finished in fourth and fifth place respectively in the same race.
Both swim for the Toronto Titans.
Sjöström's team won the match
In the 100 meter medley, Sarah Sjöström came in third place for her team Energy Standard, only six hundredths behind the Canadian Sydney Pickrem who won in the time 58.40.
At the same distance Louise Hansson came fourth in the time 58.92.
More than five tenths behind the winner.
Sjöström's team also won the 4x100 meter medley in superior style.
Barely two seconds before the London Roar.
The competitions in Naples, which started yesterday and ended today, were won by Energy Standard.
The team collected a total of 568 points.
MORE SWIMMING: Different worlds for Brazil star and Afghan debutant in Paralympics (August 29, 2021)
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Different worlds for Brazil's star and Afghan debutant Photo: Bildbyrån / SVT