East Bengal went ahead with a James Moga header in the 39th minute while Bagan restored parity in the 67th minute when C S Sabeeth headed home from a drop ball from opponent keeper Gurpreet Singh.
Both now have 20 points each. East Bengal have played 14 games while Mohun Bagan had four more games.
While Bagan's goal machine Odafa Okolie was still nursing with a hamstring injury forcing coach Karim Bencherifa to try out with new striking line of Ram Malik and substitute Manish Bhargav, Armando Colaco had tough time to have replacement for Uga Okpara and Edeh Chidi in the first eleven.
East Bengal surged ahead in a counter attack six minute from the break when Moga headed home a left cross from Joachim Abranches as Bagan keeper Shilton Paul failed to read the floater.
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After resumption, Bagan upped the ante for an equaliser with short passes as their midfielder Katsumi Yusa was the live-wire in the attack. His two shots were saved by Gurpreet Singh.
Bagan coach Karim Bencherifa made two changes bringing in Manish Bhargav in place of Ram Malik and Pritam Kotal to replace Shouvik Ghosh. With fresh legs, Bagan attack got momentum, especially long ranging shots from Bhargav.
In the stoppage time East Bengal's Ryuji Suoka had another chance but his shot went over the bar.
Bencherifa expressed happiness with his boys' performance, while his rival coach Armando Colaco was disappointed, saying East Bengal were out of the title contest now.