In the contest played at the SuperSport Park, the 22-year-old left-hander got to the triple figure mark in 51 balls.
India suffered an early blow as Sanju Samson was dismissed for a naught by Marco Jansen in the first over.
Nevertheless, skipper Suryakumar Yadav decided to promote Tilak up the order and he succeeded to prove his metal. He forged a 52-ball 107-run partnership with fellow leftie Abhishek Sharma to steer India to 100 runs in just 8.1 overs.
The Proteas clawed back into the game with two quick wickets as Abhishek and Suryakumar departed in the span of two overs. But Tilak stood his ground and partnered up with Rinku Singh as they added 58 runs in just 30 balls for the fifth wicket partnership. Rinku played the second fiddle as Tilak did most of the heavy-lifting, contributing 45 runs in the partnership.