Sabalenka, who was runner-up in Indian Wells earlier this month and at January's Australian Open, refused to accept the consolation trophy this time as she closed it out with a superb backhand shot down the line and thrust her hands in the air.
Fourth seed Pegula has been hungry for revenge since losing to Sabalenka in her maiden Grand Slam final in New York last year but the 31-year-old could not match the Belarusian's raw power as she lost momentum after a promising start.
The rivals traded breaks three times in the first set before Sabalenka clinched the critical break with inspired play in the final game, sending a scorching winner down the line before forcing Pegula into a forehand error on set point.
The American was at her best when she forced the 26-year-old Belarusian to sprint back and forth on the baseline in the opening game of the second set and broke with a backhand winner.
But Sabalenka quickly subdued Pegula with her power, levelling it in the second game.
Pegula saved three break points in the fourth but boiled over with frustration, thrusting her racquet to the court, after allowing Sabalenka a fourth break point chance that the Belarusian converted with another winner.
Sabalenka converted yet another break to clinch the match and was apologetic in her trophy ceremony after a rain-dented Saturday saw the home hope denied.
"Thank you that the rain stopped - it felt like Miami was crying that I won this tournament," the Belarusian said.
Sabalenka never dropped a set en route to the podium, beating the former champion Danielle Collins in the round of 16 before overcoming the Olympic champion Zheng Qinwen in the quarters and the sixth seed Jasmine Paolini in the semi-final.Â
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