A spectacular volley from Jose Ramirez Barreto gave Mohun Bagan a solitary goal win over Thailand's Osotpa M-150 FC in an AFC Cup Group F return leg tie in Kolkata on Tuesday.
The Brazilian's strike, coming a minute into the second session, took Bagan to the top of the group with eight points from four games.
A long ball from midfield meant for Baichung Bhutia saw the lethal Sikkim striker missing a header. Barreto, who was following the ball, fired a rasping volley from the edge of the box into the corner of the net.
The Salt Lake stadium exchange saw Bagan controlling the proceedings for most part of the 90 minutes, but the wastefulness of their strikers prevented the local side from increasing the margin.
Mohun Bagan put up a good show as they played as a team, with their medios combining well with the upfronters.
The young team from Thailand paid for their inexperience and were forced to defend their citadel for the bulk of the match.
The two sides had finished goalless when they met in the first leg in Thailand.
Osotpa are now on four points from as many games.