A laser-focussed Osaka held serve throughout and fired nine aces in a surgical takedown to kick off her return to Flushing Meadows following a maternity leave year off in 2023.
Miscues including six double faults and 21 unforced errors plagued an uneven performance by the hard-hitting Latvian.
A back-and-forth first set turned in Osaka's favour as Ostapenko hit a cross-court backhand into the net in the eighth game, earning the four-time major winner the first of her three service breaks.
Former world number one Osaka gave a friendly New York crowd a glimpse of her past dominance in the second set as she blasted three straight aces to claim the fourth game.
Ostapenko fought off two match points before Osaka slammed the door with a blistering cross-court forehand winner, setting up a second-round bout with Karolina Muchova.
An emotional Osaka said the adoring New York crowd fuelled her from the moment she stepped out on the court in a ruffled skirt and a jacket, shoes and headphones adorned in matching green bows.
"I was trying not to cry when I was walking out," she said.
"I remember last year I was watching Coco play and I so badly wanted to step on these courts again and I didn't know if I could."
Her emotional return to the tournament she won in 2018 and 2020 was nearly derailed by an uncooperative one-year-old.
"Last night, my daughter didn't want to go to sleep on her bed time so I had to hold her for quite a while. I was like, oh wow, she really picked the perfect day not to go to sleep."
--Reuters--