Starting the game on a rousing note against the 2014 I-League champions, Mumbai took the lead in the fifth minute when Arata Izumi slotted home from close range after a goal-mouth melee.
It was a defensive error as the cross from the right flank sent by Jayesh Rane was let through for Sushil Kumar Singh and Eric Brown to take pot shots only for the ball to rebound into play before Izumi finished it by beating the goalkeeper at the near post.
Mumbai FC totally dominated the first half and should have scored two more goals but for Sushil Kumar Singh and Ryuki Kozawa being off the mark with only the keeper to beat.
The visiting team, which suffered their first loss after three straight wins, made two substitutions in the second half with skipper Sunil Chhetri and Alwyn George being replaced by Thoi Singh and Udanta Singh.
Mumbai FC defenders, led by Son, totally bottled up Bengaluru's Korean striker Kim Song Yong, who had scored twice in their previous game against Shillong Lajong.
The others did not have the creative ability to break through the stubborn Mumbai FC defence in which Son and Pratik Chowdhary stood out.
The victory enabled Mumbai FC to leapfrog from fifth to the second spot with two wins and as many draws (6 points) while Bengaluru remained on top with nine points.
