The UP side chased down the target of 128 with three balls to spare, reaching 129 for 5 in 19.3 overs.
Grace Harris top-scored for UP Warriorz with 39 while Tahlia McGrath contributed 38.
For Mumbai, Amelia Kerr took two wickets for 22 runs.
This was MI’s first defeat in the league.
Brief Scores:
Mumbai Indians: 127 all out in 20 overs (Hayley Matthews 35, Issy Wong 32, Sophie Ecclestone 3/15).
UP Warriorz: 129 for 5 in 19.3 overs (Grace Harris 39, Tahlia McGrath 38; Amelia Kerr 2/22).