The teams fought toe-to-toe right until Roy Krishna's header decided the fate of the game in the final minute.
Antonio Lopez Habas and Stuart Baxter made a change each to the lineups. Manvir Singh replaced David Williams and Diego Mauricio came in for Manuel Onwu for ATK Mohun Bagan and Odisha respectively.
The first major goal-scoring chance fell to Roy Krishna in the 24th minute when he found himself one-on-one with Kamaljit Singh after receiving a long ball from Tiri inside the Odisha box. The Fijian blasted the ball over the crossbar.
The easiest chance of the half was squandered by Jacob Tratt in the 35th minute. Premjit Singh played a short corner to Marcelinho who found Cole Alexander at the edge of the box. Alexander lobbed a cross into the box for Tratt who headed wide with an empty net available.
The first half was a cagey affair and an evenly poised contest as both teams adopted a safety-first approach.
ATK Mohun Bagan were unlucky not to get a penalty in the 50th minute when Hendry Antonay brought down Prabir Das. The replays suggested that the tackle was just inside the box but the referee awarded a free-kick instead.
In the 56th minute, Prabir Das' cross into the box was only half-heartedly cleared by Steven Taylor. The ball hit Manvir on his left arm and fell to Cole Alexander who mistakenly headed the ball into his own net . Manvir was punished for a handball and the own goal was cancelled.
The Kolkata giants switched gears and commanded proceedings but were not able to create cleat-cut chances in the attacking third.
But the Mariners finally broke the deadlock and sealed the fate of the game in the final minute and Roy Krishna proved to be their saviour yet again. Tiri floated a long free-kick into the box and Sandesh Jhingan headed the ball into the middle from the right side. Krishna rose above Alexander and found the back of the net with a glancing header.