Ranti Martins and Chidi Edeh struck a brace each to outplay Sur Club of Oman 5-2 in their final Group A match and take their side to their maiden AFC Cup quarter-finals in Margao on Wednesday.
Captain Martins led from the front to score in the 30th and 38th minutes while his strike partner Chidi Edeh found the target in the 64th and 90th minutes. India midfielder Climax Lawrence contributed with one goal in the 72nd minute.
Mohammad Salim Mohammed (75th) and Al Harbi Saleh Rashid (86th) scored for the visiting side.
With 10 points from six matches, Dempo have ensured a place in the quarter-finals of Asia's second tier club competition even though the other match of the group between Al Muharraq (8 points) of Bahrain and Al Ansar (8 points) of Lebanon has been postponed due to security reasons.
Five group toppers and three best second-placed teams make it to the knock-out stage and the I-League champions will make the grade either as Group A toppers or second-placed team.
The second placed teams from Group D and E will also qualify for the last eight while the second placed teams from Group B and Group C will not make the grade.
Another Indian club East Bengal, who needed a win for any chance of qualifying, lost to Ahli Sana'a of Yemen 0-1 on Wednesday in Group B.
Dempo had failed to get past the group stage of the competition in two earlier occasions in 2005 and 2006.