[2] The draw for the third round was held on 23 April 2021, 14:00 at CBF headquarters in Rio de Janeiro.
[3] In a first draw, the 32 teams, seeded by their CBF ranking, were drawn into 16 ties.
If the aggregate score was level, the second-leg match would go straight to the penalty shoot-out to determine the winners.
Tied 1–1 on aggregate, CRB won on penalties and advanced to the round of 16.
Vasco da Gama won 2–1 on aggregate and advanced to the round of 16.