Goals from Wedson Anselme (13th minute penalty) and Willis Plaza (80th) ensured the win for the away side with Gouramangi Singh's equaliser (64th) going in vain in the end at the Balewadi Sports Complex.
It took the red and gold brigade 15 minutes to take the lead when Wedson was felled inside the box by home goalkeeper Soram Porei resulting in the referee awarding the visitors a penalty.
While Porei was booked for his offence, Wedson slotted the ball down the middle with the keeper diving to his right to mark his maiden goal for the club.
Wedson looked in sublime form as he troubled Porei again 10 minutes later with a rasping strike after a solo run into the area.
DSK were pushed to the brink and could only muster a shot on target in the 36th minute. Former East Bengal winger Sanju Pradhan picked out a rising Kim Seong Yong with the striker heading at the upper frame of the goal for an alert T.P. Rehenesh to tip it over for a corner.
East Bengal had another chance to double their tally in the dying minutes of the first half as Wedson curled a 20-yard free kick inches wide of the target.
In the second period, the home team found joy when Gouramangi made the most of a rebound insde the box to sweep home and level things.
But Plaza, like Wedson scored his first goal for the Kolkata side with a low strike to the left of Porei's goal.
At Bengaluru, a barren first half made way for an entertaining second as the home team took the lead via substitute Norales who scored from close off a free kick.
Within two minutes, another substitute Vineeth side-footed a Udanta Singh assist neatly to put the match to bed.