Playing only his second Test since his match-winning debut against Zimbabwe at Harare last year, the 25-year-old dismissed opener Murali Vijay in the morning session before claiming three more wickets after lunch to put South Africa in the box seat.
Ajinkya Rahane was batting on 31 at tea which was called soon after Wriddhiman Saha's dismissal.
Home captain Virat Kohli won his fourth successive toss in the series and opted to bat on a track which wore cracks but looked hard, unlike the rank turners used in previous Tests.
Vijay (12) enjoyed a slice of luck after he edged Kyle Abbott to slip and began to trudge towards the pavilion when match officials, after several TV replays, decided the bowler had marginally overstepped.
Not that the right-hander could make the most of the reprieve, pushing at a Piedt delivery that reached Hashim Amla in the slip.
Piedt struck early in the second session, trapping the set Shikhar Dhawan (33) leg before wicket while Abbott bowled out Cheteshwar Pujara (14) in the next over to peg back the hosts.
Kohli (44) and Rahane did not look perturbed though, and boundaries started flowing from their blades as they negated the South African bowlers with consummate ease.
The duo had raised 70 runs in 17 overs when Kohli fell to Piedt, sweeping the spinner straight into the body of Temba Bavuma at short leg.
The ball ballooned up after hitting the evading fielder on his thigh and wicketkeeper Dane Vilas sprinted from behind the stumps before diving full stretch to take the catch.
Rohit Sharma was scoreless when he edged Abbott to Amla at slip but the South African skipper dropped him. The batsman could not add to that scratchy single and hoicked the first ball of the next over from Piedt to Imran Tahir at long on.
Abbott claimed his second wicket by breaching Saha's defence to consolidate South Africa's position at the stroke of tea.
The visitors brought in Bavuma, Abbott and Piedt for Stiaan van Zyl, Kagiso Rabada and Simon Harmer, while India, who have taken an unassailable 2-0 lead in the series, left out leggie Amit Mishra and drafted in paceman Umesh Yadav. – ReutersDane Piedt dazzled in his Test return, wrecking India's top order to reduce the hosts to 139-6 at tea on the opening day of the fourth and final Test.
Original source: Piedt has India in a spin