It was the 27-year-old Japanese player's first WTA title since she became a mother in July 2023.
"Kinda ironic to win my first trophy back on the surface that I thought was my worst. That’s one of my favourite things about life though, there’s always room to grow and evolve," Osaka posted on X.
Osaka struggled with her lack of power and accuracy as she failed to progress beyond the second round of any Grand Slam last year.
The former world number one, who reached the third round of the Australian Open in January, is set to feature in the main draw of the French Open later this month.