Opener Dean Elgar smashed a century before Sri Lanka pegged back South Africa with four key wickets late on the opening day of the first Test in Galle.
The visitors were cruising at one stage after a cracking 103 from Elgar and a sedate 80 from Faf du Plessis.
But the hosts fought back in the final session to restrict South Africa to 5-268 at close of play on Wednesday.
Quinton de Kock (17) and Dale Steyn (0) were the not out batsmen.
Elgar, 27, hit 11 fours and three sixes in his 186-ball knock but his dismissal immediately after the tea break triggered a mini-batting collapse that handed the advantage to the hosts.
"I felt our bowlers bowled really well on a batsman-friendly wicket," Sri Lanka's bowling coach Chaminda Vaas said.
"They kept their cool and bowled extremely well. Hopefully, now we can wrap it (South African innings) up in the first session tomorrow."
Hashim Amla, leading the side for the first time in Test cricket, had a forgettable outing as a batsman and made just 11 off 36 balls.
Du Plessis holed out to Kaushal Silva off slow bowler Dilruwan Perera, and the in-form AB de Villiers (21) was bowled by Lakmal with the new ball in the penultimate over of the day.
The day belonged to Elgar, who shared a 70-run opening stand with Alviro Petersen (34) and another of 125 with du Plessis for the second wicket.
Elgar, playing his 10th Test, reached his second century in style, dancing down the track to smack Perera (2-100) for a massive six over the fence.
The visitors' dressing room erupted in applause for what was the first ton by any South African opener on the island.
Elgar said the rest of the batsmen would have to work really hard because the wicket had already deteriorated quite considerably.
"We'd have loved to have been three-down at the end of the day. But we have batters in the shed who all know how to play their shots," he said.
"It's going to be a lot of hard work, especially with the wicket deteriorating quickly."
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