Spanish striker Sergio Mendigutxia's 49-minute penalty helped them edge Sreenidi Deccan.
Gokulam scored a 4-1 win in the I-League in New Delhi.
Punjab crushed Rajasthan United 4-0 to seal the title with a match to spare.
The defending champions lost 0-1 while TRAU climbed to fourth with the win.
Gokulam remain in third spot with 33 points from 19 games.
Gokulam jumped to third place with 27 points from 17 matches.
The match ended 2-1 in favour of the Kolkata side leaving Gokulam fourth in the table.
The win helped Punjab tie with Sreenidi Deccan on points (34) at the top of the table. Deccan are ahead on goal difference.
The defeat meant Gokulam could not capitalise on RoundGlass Punjab FC dropping points after conceding a last-minute equaliser to bottom-placed Sudeva Delhi.
Gokulam were reduced to 10 men in the 56th as Rahul Raju was sent off.