With two runs needed off the final delivery, Malinga executed a slower yorker to perfection, trapping Shardul Thakur (2) right in front to send his teammates, including skipper Rohit Sharma, into delirium as Shane Watson, whose breathtaking 80 went in vain, sunk in his seat in the Chennai dugout.

Chasing a modest 150 for victory, Watson, who was dropped on 56 by Rahul Chahar, carried Chennai's hopes with a belligerent 80 off 59 balls, his innings laced with eight fours and four sixes.

But once he was run out in the fourth ball of the final over, it was Sri Lankan Malinga who showed his class to snatch the crown from the defending champions.

In the last five overs, Chennai needed 62 off 30 balls. Watson then hit Malinga for a hat-trick of fours to trim the equation to 42 off 24 balls.

There was no stopping the veteran Australian, who scored a hundred in the final to help Chennai win the IPL last year, as he clobbered Krunal Pandya for three back-to-back sixes in the 18th over which costed Mumbai 20 runs.

Mumbai's best bowler Jasprit Bumrah (2/14) then bowled a brilliant penultimate over, sending Bravo (15) back in the hut after the latter gave Quinton de a simple catch behind the stumps. However, de Kock missed an easy gathering to gift Chennai four byes in the last ball of the over.

Earlier, Faf du Plessis (26) and Watson gave Chennai a steady start before Krunal got the former stumped by de Kock by luring him to come down the wicket.

With du Plessis gone for 26 off 13, Watson and Suresh Raina (8) shared a 37-run stand for the second wicket as Chennai looked to be cruising.

Rohit then gave the ball to Rahul Chahar (1/14) who started Chennai's downfall by trapping Raina (8) in front. Ambati Rayudu (1) could not add much to the tally, getting caught behind off Bumrah.

The game-changing moment came in the 13th over when M.S. Dhoni (2) was caught short of the crease by Ishan Kishan, with replays showing it to be a close call.

Watson and Bravo then joined hands for a 51-run partnership for the fifth wicket which was finally broken by Bumrah. From there on, it was a see-saw battle which eventually saw Mumbai continue their dominance over Chennai in what was their fourth final meeting.

Earlier, Deepak Chahar (3/26) and Imran Tahir (2/23) starred with the ball as CSK restricted MI to 149/8, even as Kieron Pollard hit an unbeaten cameo (41* off 25) down the order.

Pollard, who was dropped on 25 by Suresh Raina, was the top-scorer for Mumbai as he hammered three fours and three sixes. For Chennai, Shardul Thakur also picked up two wickets for 23 runs.

But Pollard hogged the limelight for the wrong reasons in the last over when as a mark of protest against the umpire not calling a wide in the previous delivery, he walked across -- even leaving the pitch -- to face the fourth ball before Dwayne Bravo pulled out.

Opting to bat, Mumbai were off to a flying start riding on de Kock's power hitting. The South African stumper-batsman took on in-form Deepak Chahar in the third over, smashing three sixes to take 20 runs off it.

de Kock looked to be in the mood as he slapped Shardul for a six in the fifth over. But the pacer had his revenge in the next ball when he cramped de Kock for room with a quick delivery that the batsman lobbed to Dhoni who took an easy catch. de Kock clobbered four sixes en route his 17-ball 29.

In the next over, Dhoni became the wicket-keeper with most dismissals in IPL history when he dived forward to take Rohit's catch off Deepak Chahar who outfoxed the Mumbai captain with a knuckleball. Rohit's patchy form in the IPL continued as he could only manage 15 off 14 balls, hitting one four and a six.

Mumbai, who suddenly seemed to be in some sort of trouble at 45/2 after the Powerplay, were dented further by Imran Tahir who accounted for Suryakumar Yadav (15), the star of Mumbai's last game, and Ishan Kishan (23) as Krunal Pandya (7) was sent back in between by Shardul who took a brilliant catch off his own bowling.

With five overs remaining, Mumbai were 102/5 but Deepak Chahar's brilliance restricted them to a score of below 150 despite Pollard smashing two fours off the last two deliveries.

Brief scores: Mumbai Indians: 149/8 in 20 overs (Kieron Pollard 41 not out, Quinton de Kock 29; Deepak Chahar 3/26, Imran Tahir 2/23); Chennai Super Kings: 148/7 in 20 overs (Shane Watson 80, Jasprit Bumrah 2/14)