In ideal playing conditions on the sun-kissed Court Philippe Chatrier, Barty was often left stranded on the red clay by the big shots of her American rival. But two years after claiming the French Open title, the Australian top-ranked player fought hard enough to overcome the challenge and eventually prevailed 6-4, 3-6, 6-2 on Tuesday.
As Pera lost her focus and hit 19 unforced errors in the deciding set, Barty made up for her lack of mobility with clever combinations of lobs and angled shots. She played with her left thigh bandaged and received medical treatment after Pera leveled at one set apiece.
"I just keep fighting, I just keep trying," Barty said after improving her three-set match record to 12-2 this year.
Barty decided not to defend her title last year because of the coronavirus pandemic. In the buildup to the French Open this year, she played 13 matches on clay, winning 11. But she was forced to retire in the quarterfinals in Rome because of an injury to her right arm, raising concerns about her condition ahead of the tournament in Paris.
"It's going to be a little bit tough this week," she said. "I think over the weekend we had a bit of a flare-up through my left hip, which obviously just needed a bit of help today, needed some assistance to try and release it off as best I could."
The seeded players in the women's draw scheduled early in the day had solid starts to the event. Fifth-seeded Elina Svitolina trailed 5-2 in the second set but beat wild card Oceane Babel 6-2, 7-5. Australian Open runner-up Jennifer Brady breezed past Anastasija Sevastova 6-3, 6-3 to reach the second round and match her best performance at the French Open.
Two-time Wimbledon champion Petra Kvitova pulled out of the tournament because of an ankle injury. Kvitova said she fell and hurt her ankle during "post-match press requirements" after her first-round victory Sunday. The 11th-seeded player saved a match point before coming back to beat Greet Minnen 6-7 (3), 7-6 (5), 6-1.
Venus Williams lost in her opener Tuesday. She was runner-up at Roland Garros 19 years ago but has now lost her opening match at the clay-court major for the fourth year in a row.
In her 24th appearance at the French Open, the veteran American player lost 6-3, 6-1 to Ekaterina Alexandrova of Russia.
Earlier, play was briefly delayed on Court Simonne-Mathieu after a bomb scare near the stadium that turned out to be a false alarm, according to French police. A security perimeter was quickly set up as spectators and tournament employees were forced to enter the venue via another access point.
Information from The Associated Press was used in this report.