Sunrisers, led by a brisk unbeaten 63 from opener Shikhar Dhawan, and a quick-fire 36 from 16 balls from Ashish Reddy, posted a competitive 159 for six from their 20 overs in Chennai.
In response the Super Kings got off to a good start via Mike Hussey's 45, but he fell just before the halfway point of the innings.
Other batsmen came and went, and Dhoni enjoyed little in the way of partnerships. But he marshalled a chase of 30 runs from the last 14 balls, with four sixes and seven fours in his 37-ball 67, to get the Super Kings home with two balls to spare.
Chennai join Royal Challengers Bangalore at the top of the table, but the Challengers sit above them by virtue of a superior net run rate. The Sunrisers slip to third.