Jonatan Alvez put Inter ahead with six minutes remaining but Vasco drew level in injury time with a penalty from Maxi Lopez.
A win would have taken Internacional into second spot just two points off the lead.
They remain in third, behind Flamengo on goal difference and sit two points ahead of Sao Paulo, who beat Vitoria earlier. Palmeiras play Flamengo in the big game of the round on Saturday.
(Reporting by Andrew Downie; Editing by Greg Stutchbury)
