The home team, who conceded an early goal, scored the equaliser in the injury time of the first half before netting twice minutes after the break to seal a 3-1 comeback win at MA Aziz Stadium on Friday.
Abahani controlled the opening exchanges but East Bengal, who had remained unbeaten in the five-nation tournament, took the lead in the 10th minute.
Avinabo Bag tore away from a defender to enter the box from the right before unleashing a shot that took a deflection off Rezaul Karim and sailed over goalkeeper Rasel Mahmud into the net.
East Bengal, who are three-time I-League champions, took control of the midfield and came close to a second in the 29th minute but Sohel Rana blocked Md Rafique’s powerful header on the goal line.
Abahani, egged on by the partisan home crowd, gradually regained possession and kept searching for goals.
Zahid Hossain and Hemanta Vincent Biswas tried their luck with several shots but failed to beat East Bengal goalkeeper Dibyendu Sarkar. Then, Nigerian marksman Eleta Kingsley put Abahani level in the dying seconds of the first half.
Kingsley sent a powerful header past Dibyendu to restore parity in the scoreline off Zahid’s sidefooted cross.
Abahani came out all guns blazing after the break and scored twice in four minutes to virtually take the game beyond the reach of the Kolkata club.
Zahid sent a low cross that curved away from East Bengal backline to find Kingsley again.
The African scored his second of the match and fifth of tournament with a cool finish in the 54th minute.
Kingsley was the architect of the third. Hemanta Biswas dashed into the box and rose to head Kingsley’s cross past Dibyendu in the 57th minute.
East Bengal desperately looked to get back in the match but relentless Abahani kept pressing for more.
Abahani came close to widening the gap a number of times after that but could not find the target as their attacks broke down in the final third with a tired frontline.