Put into bat, Kings XI Punjab were restricted to 138 for eight in the stipulated 20 overs at the Punjab Cricket Association IS Bindra Stadium.
Led by Uthappa's blazing knock of 53 off 28 balls, the visitors chased down the target of 139 with 17 balls to spare. KKR skipper Gautam Gambhir continued to lead the team well, scoring 34 off as many deliveries.
Uthappa reached his 50 off 24 balls, before leg-spinner Pradeep Sahu had him trapped in front of wicket to end a fluent opening wicket partnership of 82 runs in just under nine overs.
By the time Uthappa was heading back to the dugout, half the job was done for KKR, who were 93 for one midway into their chase.
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Eyeing their third win of the season, KKR required 46 runs in the back 10 with Gambhir in control of the proceedings.
But just then, Gambhir fell to a brilliant catch by Glenn Maxwell, who ran in from the boundary to hold onto the ball. As Gambhir hit the ball in the air, there was no one at midwicket area, and it looked like it would fall in no man's land. But Maxwell anticipated well and timed his full-stretched dive to perfection and pulled off the catch inches from the ground.
Owing to Uthappa's assault, Kings XI Punjab bowlers Sandeep Sharma, Kyle Abbott, Mohit Sharma and Maxwell conceded nearly 20 each in their first two overs.
Sahu was the most impressive of KXIP bowlers, returning figures of 2/18 in four overs. Axar Patel went straight through the defence of Manish Pandey (12) to KXIP their third breakthrough.
Shakib Al Hasan (11), who got a life when Manan Vohra made a mess off an easy chance at long-off, got out the very next ball when he skied one to Sandeep Sharma off Patel.
Earlier, Shaun Marsh top-scored for the hosts with an unbeaten 56 off 41 balls. The Australian struck five boundaries and a six during his stay in the middle in a rather mediocre outing by the Kings XI Punjab batting line-up.
For KKR, Sunil Narine finished with impressive figures of 2/22, while Morne Morkel had 2/27 from their quota of four overs each.
There was wicket apiece for Umesh Yadav, Piyush Chawla and Yusuf Pathan.
The total could have been much less had it not been for the 18 runs Marsh and Kyle Abbott (12 not off six balls) plundered in the innings's last over bowled by Andre Russell.
Experienced opener Murali Vijay spent some time in the middle, but could not manage more than 26 runs in 22 balls before being foxed by a Piyush Chawla googly.
Wicketkeeper Wriddhiman Saha (8) did not last long and became Sunil Narine's first victim since his comeback as the ace spinner had the batsman caught behind.
The hosts were dealt a body blow when off-spinner Yusuf Pathan had skipper David Miller (6) caught behind with a delivery that cramped him for room.
Even as the slide continued for Kings XI Punjab, Shaun Marsh held one end firm through singles, twos and the occasional boundaries.
Looking for their second win of the season, what badly affected the home side was the lack of partnership through the innings, thanks to the failure of its star batsmen at the Punjab Cricket Association IS Bindra Stadium. 26 was the highest partnership of the innings.
Axar Patel displayed poor temperament and was dismissed by Umesh Yadav's slow off-cutter. Marsh broke the silence in the stands with a spanking pull shot off Morne Morkel.