Norde picked up the ball near the centre line six minutes from the end during a counter-attack and produced a speedy run down the left before coming up with an excellent finish.
The goal came as a relief for Mohun Bagan fans after they witnessed their team struggle in front of goal for an agonising 84 minutes.
The result saw Mohun Bagan notch up 33 points from 16 matches, the same as second-placed Aizawl FC.
But Mohun Bagan took the top spot thanks to a better goal difference and head to head record.
Earlier on Saturday, Kamo Stephane Bayi scored once in each half as Aizawl FC beat Churchill Brothers 3-1 in Goa.
Bayi scored in the seventh and 46th minutes while Robert Laldanmawia (84th minute) got Aizawl's third goal right in the closing stages as Aizawl temporarily climbed to the top of the standings with 33 points from 16 matches.
Anthony D'Souza scored for Churchill in the 68th minute. Churchill are sixth with 17 points from 16 matches.
Churchill who got the first chance of the game when Meldon D'Silva curled in a free-kick into the Aizawl penalty box and Chesterpoul Lyngdoh crashed his header against the bar.
The hosts will be left to rue that missed chance a few minutes later when Brandon Vanlalremdika and Bayi combined superbly inside the opponent penalty box before the latter fired the ball between the legs of Churchill goalkeeper Naveen Kumar.
Churchill enjoyed quite a bit of possession, trying to hold the ball in midfield and looking for the openings.
But the hosts were let down by a lack of quality of the final ball. Churchill strikers Anthony Wolfe and Ansumana Kromah also showed a marked lack of coordination.
Bayi scored his second goal right after the restart when he received Brandon's pass before beating Naveen with an excellent finish.
Churchill reduced the deficit to one when Wolfe played to Anthony from the left and the latter produced a calm finish.
Robert put the issue beyond doubt when he fired home a powerful shot from the top of the box.
Meanwhile in Shillong, defending champions Bengaluru FC beat Shillong Lajong 2-0 to lift themselves to the fourth spot due to their better head-to-head record over the hosts.
Skipper Sunil Chhetri (26th minute) and Harmanjot Khabra (49th) were the scorers for Bengaluru, who secured their second win on the trot to make it 24 points from 16 matches.
The visitors had beaten Aizawl FC in a home match before coming for the Shillong tie.
Lajong, meanwhile, will have their task cut out in the remaining two matches if they still fancy a top three finish in the season. They have dropped to the fifth spot with 24 points.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)