Sabalenka, who missed Wimbledon with a shoulder injury, had lost two Masters finals to Polish star Swiatek already in 2024.
It was a different story on Sunday and despite Sabalenka needing 11 match points, she eventually sealed victory in one hour and 48 minutes with a superb backhand winner to clinch a 6-3 6-3 victory.
"I wasn't over-rushing things. I was trusting myself a lot, and I wasn't trying to over-hit the ball," Sabalenka said.
"I was just trying to stay there, put as much pressure as I can on her, and I was really focused on my serve."
The Belarusian will return to number two in the rankings with this result but will eye a first title since her second consecutive Australian Open success in Monday's final.
American Pegula denied Sabalenka the chance to take on best friend Paula Badosa after she won a tight three-setter with the Spaniard.
Sixth seed Pegula claimed the opener and forced an early break in the second before Badosa, who has impressed during the second half of the season, fought back.Â
Rain briefly halted proceedings, but it was Pegula who prevailed 6-2 3-6 6-2 to set up a seventh meeting with Sabalenka.
For Pegula, who won the Canada Open last week, it was her ninth consecutive victory. She will now aim to become the first woman since Evonne Goolagong in 1973 to win the Canada and Cincinnati titles in the same year.
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