Vasco played a cohesive game with their strikers and midfielders striking the right cord but lack of finishing proved to be their undoing as they wasted several scoring chances in the first half despite dominating it.
Despite their opponents being reduced to ten men five minutes before the end, Dempo failed to capitalise on the advantage. The only close chance they had was in the injury time of the first half when a R C Prakesh shot was saved by a diving keeper Ramos.
Brazilian Marcos Pereira, playing his first match for Vasco after shifting from Mohun Bagan, played the dominating role along with Nigerian Amaechi Tochukwu. He had two chances to score but missed both. First he failed to guide the ball and then saw his kick saved by a dive by keeper Mondal.
Vasco who drew their second successive match have collected 8 points from seven matches while Dempo who remained unbeaten so far are on top with 17 points from 7 matches.
Referee S Suresh showed yellow cards to Vasco's John Dias and Dempo's Sunday Seah.
Vasco probed into the rival half more often creating at least five chances but were denied by Mondal who made three good saves to deny his opponents full points.
Vasco's best chance to forge ahead came midway into the first half when Denis Cabral laid a pass to Amaechi, but Alter who was unmarked inside the box ballooned the ball over the bar.
After the change of ends, Vasco continued to dictate terms and had two scoring chances but first a Marcos shot was well collected by Mondal and later substitute Levy Coelho was late in connecting the ball off a throw by Selwyn Fernandes.
With five minutes to go, Vasco were reduced to ten men when John Dias got his double booking from referee Suresh for a foul on Raju Singh.