After conceding first from a Katsumi Yusa penalty, Sandesh Jhingan and Sunil Chhetri scored a goal each to help Bengaluru pick up all three points in the opening match of the 2017 AFC Cup.
Bengaluru coach Albert Roca made two changes to the starting XI, bringing in C.K. Vineeth and Salam Ranjan Singh ahead of Eugeneson Lyngdoh and Nishu Kumar as the hosts started out with what looked like a 4-2-3-1 formation.
The hosts had an early scare when goalkeeper Arindam Bhattacharya, under pressure to get rid of a back pass, could clear only as far as Katsumi Yusa. The Bengaluru defence had to rush back in numbers and stuff the danger out.
But just when it seemed like the teams would hit the showers without anything to show for their efforts in the first half, the visitors were awarded a penalty in the 35th minute when Jhingan's trailing leg caught Mohun Bagan winger Sony Norde in the penalty box.
Arindam picked the right side but Yusa's take was hit with enough power to fly beyond him and give the Kolkata club the lead.
Finding themselves down by a goal, Bengaluru decided to dig deep and own the second half like a team possessed.
Eugeneson Lyngdoh came on for Lenny Rodrigues as the hosts began pegging the Bagan defence back. And in what was poetic justice, Jhingan hit home Bengaluru's equaliser from a well-worked set-piece in the 51st minute.
Making a late run into the visitors' penalty box, the defender met Cameron Watson's corner with a sweet hit that flew past the defence and Mohun Bagan goalkeeper Shilton Paul as the Kanteerava erupted.
With their tails up and sensing fear in the Bagan ranks, Bengaluru constantly invaded the Mariners' box with darting runs from either flank.
In the 57th minute, Shilton stepped out of the box with the ball in his hand, giving the Blues a freekick in a dangerous position. Chhetri made no mistake with his effort, which pried through the Bagan wall and found the net to send the Blues faithful into frenzy.
Bengaluru had numerous chances to extend their lead. Vineeth's cross for Lyngdoh was inches away from the midfielder's diving header before a miscued effort from Daniel Lalhlimpuia saw the ball fizz past Paul's frame. A free-kick from Juanan seemed like the icing on the cake for the hosts but his take was inches away from the Bagan crossbar.