Chasing a score of 139 runs, RCB were skittled for 119 runs, their fourth bowl out this season.
Earlier, the RCB skipper Virat Kohli won the toss and put the visiting side to bat first, who managed 138 runs for the loss of seven wickets.
Among the Punjab batsmen, Shaun Marsh (20), Manan Vohra (25) and Wriddhiman Saha (21) each got off to a start but failed to capitalise on it.
However, a rearguard action from allrounder Axar Patel, who contributed 38 runs off 17 balls, helped the Punjab side get to their eventual score.
Patel was later instrumental with the ball too and claimed three wickets.
Chasing the target, RCB lost wickets early as Chris Gayle (0), Virat Kohli (6) and AB de Villers (10) were all sent back to the pavillion by Sandeep Sharma, who was adjudged the Man of the match for his exploits with the ball.
The rest of the RCB batsmen apart from Pawan Negi (21) failed to rally around for long as they lost their fifth consecutive game in the 10th edition of the IPL.
image: IPL Twitter account