Aser Dipanda's 39th-minute strike pulled the visitors ahead but Anthony Wolfe (78') restored parity for the hosts in the second half.
Churchill Brothers coach Petr Gigiu made three changes to his side that lost 3-2 against Shillong Lajong. Khalid Aucho returned from injury alongside Nenad Novakovik to replace Rowilson Rodrigues and Nicholas Fernandes while Vigneshwaran Baskaran stepped in for James Kithan in between the sticks.
On the other hand, Mohun Bagan's Khalid Jamil rang in four changes. In came Mehtab Hossain, Bikramjit Singh, Abinash Ruidas and Amey Ranawade in place of Shilton D'Silva, Lalchhawnkima, Azharuddin Mallick and Arijit Bagui.
The visitors had an early opportunity as Baskaran blocked Dipanda's shot from close range but the ball fell to Norde who shot wide in the third minute.
For the hosts, Hussein Eldor got closest to scoring a goal in the 17th minute when his free-kick had goalkeeper Shilton Paul beaten but the framework came to his rescue and the ball rattled off the woodwork.
The hosts were then jolted by two quick injuries to Richard Costa and Eldor before a defensive lapse by the latter's replacement in Rowilson handed Bagan the opener. Dipanda was at hand to take advantage and slot the ball past Baskaran after the ball was headed towards him by Henry Kisekka.
Wayne Vaz put in a timely intervention to prevent Norde from receiving a cross from Dipanda from the right in the 53rd minute while Plaza was outfoxed by by Bikramjit Singh and Eze Kingsley at the edge of the Bagan box a few minutes later.
Just as Mohun Bagan looked like they would seal a win, Eze Kingsley fouled Anthony Wolfe inside the box and the Trinidadian striker converted from 12 yards in the 78th minute to rescue a point for his side.