Chandigarh - India's bowlers restricted South Africa to 149 for five despite an attacking half-century from skipper Quinton de Kock in the second Twenty20 international in Chandigarh on Wednesday.
Medium-pace bowler Deepak Chahar returned figures of 2-22 from his four overs to play a big part in choking South Africa's flow of runs after de Kock's 37-ball 52.
De Kock, a wicketkeeper-batsman, got the Proteas off to a strong start as he put on a crucial 57-run second-wicket stand with debutant Temba Bavuma, who made 49, after being put in to bat first.
The left-handed opener, who was recently appointed leader of the T20 side, smashed eight fours as he completed his third fifty in the shortest format.
Paceman Navdeep Saini got the prized wicket of de Kock with India captain Virat Kohli taking a sensational one-handed running catch from mid-off.
South Africa lost another wicket five balls later as Ravindra Jadeja sent back Rassie van der Dussen for one with his left-arm spin to check the batting team's charge.
Bavuma went on to make 49 off 43 deliveries before becoming Chahar's second victim of the evening as South Africa lost steam in the middle overs.
Unbeaten batsmen Dwaine Pretorius, on 10, and Andile Phehlukwayo, on eight, finished off in style with a six each to make South Africa get 16 runs from the final over.
Both teams are looking to go one-up in the three-match series after the first game was washed out without a ball being bowled in Dharamsala on Sunday.