The 28-year-old Pliskova had also struggled with unforced errors in her opener against Egyptian qualifier Mayar Sherif but managed to get through that match using all her experience.
Latvian Ostapenko, who won the 2017 title as an unseeded player, remained solid throughout and did not allow a sluggish-looking Pliskova to get a foothold in the match.
“I was just trying to play my game, but I knew I had to return well today because she obviously has, like, one of the best serves on tour, Ostapenko told reporters.
“I think I was returning very well today. Also, I had to hold my serve, which I did pretty good. Also to use some drop shots, because it’s a very good shot in these conditions.”
The 23-year-old Ostapenko, ranked 43rd, was aggressive from the start as her strangely subdued opponent struggled to rein in the mistakes under the closed Court Philippe Chatrier roof.
Pliskova, known as one of the biggest servers in the women’s game, committed three unforced errors and a double fault in the opening game of the match to be broken to love.
The script did not change much for Pliskova for the rest of the afternoon.
Ostapenko went on to break three times in the first set and twice in the second to seal victory in 69 minutes.
She converted her third match point when Pliskova, who had 25 unforced errors, sent a forehand long.
The Latvian painted the red clay with 27 winners against her opponent’s nine while keeping her unforced errors to 19.
“I’m sure I could do much better. I know that she can be tough if she’s playing well, but I think everything started with me,” Pliskova told reporters, adding that she would possibly not play anymore in the 2020 season.
“Definitely I was not playing great. I think maybe the same level as the match before but of course she’s a much better player. Not much to say about this match.”
Pliskova remains the only active ex-world number one who has not won a Grand Slam.
Next up for Ostapenko in the third round will be former U.S. Open champion Sloane Stephens or Spaniard Paula Badosa.