The tournament was divided into three phases. The first phase had 19 teams divided into four round-robin groups of four and one group of three (defending champions Nacional received a bye to the second phase). Each group had clubs from two countries. The winners of each group advanced to the second phase. Five teams joined the defending champions in two round-robin groups of three. The winners of each group advanced to play in the finals. The winner of the finals, and tournament champions, are determined by points (two for a win, one for tie).
The champions and runners-up of each football association were drawn into the same group along with another football association's participating teams. Two clubs from Uruguay competed as Nacional was champion of the 1971 Copa Libertadores. They entered the tournament in the Semifinals.