Man of the Match Kingsley scored off a low but powerful header from a Sony Norde corner kick to help Mohun Bagan break an anxious 40 minutes stalemate for the former champions.
Their defence, led by goalkeeper Shilton Paul, held on to the slender lead on a day Norde and Ansumana Kromah failed to make use of the opportunities.
It was a lacklustre effort by the Khalid Jamil-coached East Bengal as Willis Plaza was off target and missed a few chances and East Bengal remained on one point.
Mohun Bagan should give credit to their goalkeeper who stood tall between the posts, ensuring they don't feel the absence of Debjit Majumder, who chose to be at ISL franchise ATK.
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Battling a step-motherly treatment, the season's first derby also made a big statement with an overwhelming attendance of 64,630 despite a 2pm kickoff.
With 10 minutes left, it was almost 1-1 when Laldanmawia Ralte cut in from the left and curled one in from 10 yards away, but a cool-headed Paul showed fine anticipation as he leaped high in the air and palmed away the danger.
Mohun Bagan were held to a 1-1 draw at Minerva Punjab as the home side equalised in the dying minutes.
East Bengal on the other hand, squandered a 2-0 lead as reigning champions Aizawl FC struck twice in the last 15 minutes to make it 2-2 at this very venue.
Earlier, Norde beautifully curved in a corner and landed clear of the defence. Kingsley was lurking at far right and capitalised on the low ball after it bounced off the pitch to find the back of the net.
Moments later, Aser Pierrick Dipanda surged in from the right, clearing the defence as he had time to put it past East Bengal goalkeeper Luis Barreto.
Mohun Bagan had their best chance in the 32minute from a powerful Kingsley header that was thwarted by Barreto and the farpost also came in way of them.
The danger was still not averted as Yuta Kinowaki found the ball in a goalmouth melee, but the Japanese midfielder failed to clear the East Bengal defence.
As Mohun Bagan dominated the first half, East Bengal too had their share of chances and looked to score in the 30th minute when Brandon Vanlalremdika attacked from the right flank to set up Willis Plaza. But the Trinidadian failed to connect, much to Mohun Bagan defence's relief.
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