[2] The draw for the group stage was held on 20 December 2017, 20:00 PYST (UTC−3), at the CONMEBOL Convention Centre in Luque, Paraguay.
Teams from the same association could not be drawn into the same group, excluding the winners of the third stage, which were allocated to Pot 4 and whose identity was not known at the time of the draw, and could be drawn into the same group with another team from the same association.
[2] The winners and runners-up of each group advanced to the round of 16 of the knockout stages.
The third-placed teams of each group entered the Copa Sudamericana second stage.
The fixture list was determined by the draw as follows:[6] The matches were played on 27–28 February, 1, 13–15 March, 3–5, 11, 17–19, 24–26 April, 1–3, 15–17 and 22–24 May 2018.