Peterson, 32, adopted the switch-hit made famous by his former countryman Kevin Pietersen after his team needed 32 off the last two overs against Kings XI Punjab on Wednesday night.
The left-hander, who said he had not even practised the shot, switch-hit the first two deliveries of the penultimate over from leg-spinner Piyush Chawla for boundaries and then pulled the third for a six.
The over produced 27 runs as batting partner Ambati Rayadu smashed the last two balls for sixes, leaving Mumbai Indians needing just five runs off the final over.
Victory was achieved with one ball to spare with Rayadu making an unbeaten 34 off 17 balls and Peterson, better known as a left-arm spinner, returning with 16 from seven balls.
Peterson, whose highest score in six Tests, 55 one-dayers and nine Twenty20 games for South Africa is 61, said he had never played the switch-hit before Wednesday night's game.
"The switch-hit was played by instinct," he said. "I had not practised them. But I am happy my innings helped the team win. It is nice to get over the line in such close games."
It was Peterson's first game for Mumbai Indians, who secured his services for a relatively modest $100,000 this season, but kept him on the bench for the first six matches.
Batting superstar and Mumbai Indians team-mate Sachin Tendulkar was delighted by the power-hitting at the end.
"The 19th over changed everything for us," Tendulkar tweeted. "It is definitely one of the most exciting overs I have seen in my life.
"Some extraordinary innovative hitting by Robin (and) unbelievably strong finish by Rayudu."
Pietersen, the South Africa-born England batsman, has been using the innovative shot for Delhi Daredevils in the Twenty20 tournament. (
