Chasing 199, MI could only muster 186 for nine to suffer yet another defeat.
Dewald Brevis top-scored for Mi with 49 off 25 balls, while Tilak Varma made 36 off 20 deliveries.
Odean Smith (4/30) shone bright with the ball for Punjab, Kagiso Rabada picked up two wickets for 29 runs.
Earlier, openers Shikhar Dhawan and Mayank Agarwal hit fine half-centuries to propel Punjab Kings to 198 for five. Dhawan (70) and Agarwal (52) shared 97 runs for the opening stand in 9.3 overs to lay the foundation for Punjab's total after being sent into bat.
Brief Scores: Punjab Kings: 198 for 5 in 20 overs (Shikhar Dhawan 70, Mayank Agarwal 52; Basil Thampi 2/47).
Mumbai Indians: 186 for 9 in 20 overs (Dewald Brevis 49, Suryakumar Yadav 43; Odean Smith 4/30).