After grabbing a four-for, Amelia hit a fluent 25-ball 31 as the defending champions hunted down the below par 127 target with 11 balls to spare.
Pacer Shabnim Ismail also hogged the spotlight with a solid opening burst, bagging superb figures of 3 for 18.
For Gujarat Giants, who finished at the bottom of the table last year, had a disappointing start to their new season as well.
Kerr first made a strong impression with her leg-spin, grabbing four for 17 that helped defending champions limit Gujarat to an under-par 126 for nine.
The New Zealand player followed that effort with a solid 31 as Mumbai overhauled the target in 18.1 overs after getting reduced to 21 for two in the fourth over.
As It Happened
Kerr received excellent support from skipper Harmanpreet (46 not out, 41 b, 5×4, 1×6)) as the pair made 66 runs for the fourth wicket.
Nat-Sciver Brunt (22, 18 balls) too played a good hand and her scoops behind the wicketkeeper for fours off pacer Leah Tahuhu were epitome of innovation and timing.
But Brunt was run out as MI were in a spot of bother at 49 for three. However, Kerr and Harmanpreet displayed excellent game-awareness to bail their team out.
With a paltry target in front, both Kerr and Harmanpreet did not have to show any unnecessary urgency.
They kept the board moving with singles and twos, while hammering those occasional boundaries. Harmanpreet sliced Katherine Bryce past point for a classy four, while Kerr lapped Tahuhu over stumper Beth Mooney’s head for a four.
However, Kerr did not last till the final lap as another attempt to play a scoop off Tahuhu saw her getting trapped in front of the wicket.
But by then she had done the job.
Earlier, Kerr and veteran pacer Shabnam Ismail (3/18) clamped down Giants with fine spells.
Ismail, who has retired from international cricket, showed that her fire had not dwindled while opening Mumbai’s bowling in the Power Play segment, dismissing Veda Krishnamurthy and Harleen Deol.
Both Veda and Deol were trapped in front of the wicket with deliveries that swung back into them at a fair clip.
Pacer Brunt jettisoned Phoebe Litchfield in the sixth over as the Giants ended the Power Play at 43 for three.
But their innings nosedived further from there as Giants failed to find a boundary in the next 44 balls, and to add to their woes, they also lost wickets at regular intervals.
Skipper and opener Mooney, who survived the initial flurry of wickets, looked to get into some sort of rhythm but her attempt to reverse-lap Ismail ended in the hands of Yastika Bhatia behind the wickets.
At 58 for five in 11 overs, the Giants were always facing an uphill climb as Mumbai bowlers tightened their grip.
Kerr further complicated their troubles, dismissing Ashleigh Gardner and Sneh Rana in the space of two balls in the 14th over as Gujarat struggled for momentum and runs.
They added a touch of respectability to the total because of the eighth-wicket alliance between Bryce (25 not out) and Kanwar (28) worth 48 runs, the biggest in Gujarat innings.
But it was way too insufficient on the night.
(With inputs from PTI)