The Romanian, a two-time runner-up at Roland Garros, found herself 5-0 down to American Alison Riske in yesterday’s opening match on Court Philippe Chatrier.
Riske went on to take the first set but Halep finally woke up and dropped just two more games in registering a 2-6, 6-1, 6-1 victory.
Halep, still hunting a maiden grand slam title, will face another American, Taylor Townsend, in round two.
Halep refused to blame the rain delay, which prevented her from playing on Tuesday evening, for her sluggish beginning.
“I had a slow start because it’s always tough to start this tournament,” she said.
“It’s a pleasure to come here and to play, so always I feel nervous at the beginning.
“But it was good that I came back so strong. I felt really well in the end of the match, and that’s the most important for now.”
Caroline Wozniacki dropped just 25 points in her lopsided 6-1, 6-0 win over qualifier and Roland Garros debutant Georgina Garcia Perez of Spain, as the second-ranked Dane easily advanced to the third round.
Wozniacki delivered a ruthless performance on Court Philippe Chatrier, limiting her mistakes to eight unforced errors. She did not face a break point and completed the win in 51 minutes. She put on a similar display in her opening match, hitting only 13 unforced errors in a straight-set victory.
Wozniacki won her first grand slam trophy at the Australian Open this year and can return to the No 1 ranking held by Halep by winning the title in Paris.
Sloane Stephens, meanwhile, has dropped only six games in her first two matches. Those victories have impressed former US Davis Cup captain Patrick McEnroe, who now believes the reigning US Open champion can claim a second grand slam title at Roland Garros.
“Just FYI. Sloane Stephens is winning this tournament,” McEnroe tweeted after Stephens dispatched qualifier Magdalena Frech 6-2, 6-2 in just over an hour yesterday.
The tenth-seeded American player, who has never got past the fourth round in her six previous appearances at the tournament, is more cautious. She missed the tournament last year and went through a stretch of poor results after winning at Flushing Meadows. She knows getting carried away would be a big mistake.
“That’s so sweet, that was nice of him,” Stephens said about McEnroe’s tweet. “I mean, I can’t predict the future, I don’t know. I would love to. We’ll see next Saturday.”
Stephens will face a more serious test in the third round against Camila Giorgi of Italy, who has lost only eight games in the first two matches. Giorgi has beaten Stephens twice in their three meetings, including a 6-3, 6-0 rout in Sydney this year on hard court
Fourth seed Elina Svitolina, of Ukraine, breezed past Slovakian Viktoria Kuzmova 6-3, 6-4, while Petra Kvitova, the Czech eighth seed, was untroubled by Lara Arruaberra of Spain in a 6-0, 6-4 victory to take her into the third round, where she will face Estonia’s Anett Kontaveit.