With 1-1 stalemate prevailing in extra time, the purple brigade edged out East Bengal 5-4 in the penalty shootout as the Maidan heavyweights continued their woeful form.
United goalkeeper Sangram Mukherjee emerged hero in the shoot out thwarting Edeh Chidi and Harmanjot Khabra's spot kicks to seal the issue.
Earlier East Bengal led with Chidi's spotkick in the 22nd minute but United equalized through Baldeep Singh's goal in the 73rd minute.
Both teams failed to find the goal in extra time to take the match to the tiebreaker.
After Chidi's miss, Cavin Lobo, Shylo Malswamtluanga, Subodh Kumar and Naoba Singh scored for East Bengal.
But United goalkeeper Sangram stood tall to deny Khabra to settle the issue.