Needing 472 for victory, Bengal folded up for 339 to give Mumbai a well deserved win on the fourth day in the Elite Division final.
Mumbai raced to their victory, taking the last six wickets for just five runs as the hosts scripted a superb comeback this season, winning the trophy after losing their first three matches of the league and being in danger of being relegated to the plate division.
The hosts rose like a phoenix, winning their last five matches including the final with a day to spare.
Set a target of 472 for a win, Bengal were kept in the run chase, with magnificent innings from Manoj Tiwari and Sourav Ganguly.
Beginning the fourth day at 98 for two with Deep Dasgupta and Manoj Tiwari at the crease, it looked like it was only a matter of time, Mumbai would get their hands on the coveted trophy.
However, the Bengal batsmen had other ideas and instead of going into their shell, they attacked whenever the opportunity presented them and kept the scoreboard moving, trying to put the pressure back on Mumbai.
Deep Dasgupta, who was 43 overnight, completed his half century in 115 balls with six boundaries. He was out soon after for 57, edging one from Wilkin Mota to the keeper Vinayak Samant, who completed a regulation catch. Bengal were then 153 for three.
Ganguly then joined youngster Manoj Tiwari and the two took the attack to the Mumbai bowlers scoring at four runs an over as both did not waste any time in punishing the loose balls.
Tiwari, infact, took a liking of the off spinner Ramesh Powar hitting the stocky bowler for two huge sixers as he raced to his 50 in just 84 balls with the help of seven boundaries and two sixes.
Ganguly, at the other end, was also batting beautifully as his off-side shots coming out from the middle of the bat and he brought up his 50 in 76 balls which included seven boundaries.