Dempo and Mohun Bagan entered the final of the 26th Federation Cup Football Championship in Bangalore on Friday.
Eleven-time champion Bagan ended the dream run of Sporting Clube de Goa with a solitary goal win, while Dempo rode on a superb hat-trick by Nigerian striker Ronty Soleya Martins to beat Tollygunge Agragami 4-3 in the other semi-final.
Goa's Sporting Clube was unlucky as they ended on the losing side despite giving a good account of themselves for most part of the match played under lights.
W Tomba Singh scored the all-important goal for Bagan in the 17th minute of the extra-time after regulation time did not yield result at Sree Kanteerava stadium.
The final will be held on December 5.
Dempo had lost twice in the final previously.
In the earlier match the striking prowess of Brazilian Cristiano De Lima Junior, who scored the other goal for Dempo, and Martins came to the fore again in an enthralling encounter.
It was Tollygunge who took the lead in the 14th minute thanks to a Surajit Bose header. Bose received a header from Tarif Ahammad off a Saumik Dey shot.
Stung by the reverse, Dempo attacked and came up with two goals to lead 2-1 by the 30th minute.
First Junior found the target after rival goal keeper Arindam Ghosh did not collect a Martins shot cleanly and the ball bounced back for Martins to score as the Tollygunge defenders were caught napping.
Nigerian striker Suleh Musah made it 2-2 for Tollygunge with a long shot, giving no chance to rival goalkeeper Satish Kumar.
But in the 45th minue, Martins's powerful shot found the target as Dempo led 3-2 at half-time.
Changing ends, the Goan team increased the lead to 4-2 with Martins scoring again.
Two minutes before the final whistle, Awoemi Isiaka scored for Tollygunge but that was not enough to stop Dempo's march into the title round.