The win helped the hosts zoom up to third spot on the table with nine points from six games while the visitors, who have six points in the kitty, slipped to the sixth position.
Mumbai City FC made a nervous start as the Delhi side kept possession for major periods of the first half.
Syed Rahim Nabi, for the second time in the tournament, picked up an injury early on and was forced off with Peter Costa coming on to replace him.
Mads Junker was, however, unable to get on the end of any of them as Mumbai custodian Subrata Paul came bravely off his line a few times to thwart any danger.
As the half progressed, Mumbai slowly began to get into the groove.
Jan Stohanzl collected the ball in midfield, ran towards the goal and unleashed a thunderous effort that sailed over the bar.