The draw for the first stage was held on 20 December 2017, 20:00 PYST, at the CONMEBOL Convention Centre in Luque, Paraguay. For the first stage, the teams were divided into two pots according to their geographical zones:
Pot A : 22 teams from Argentina, Bolivia, Chile, Paraguay, and Uruguay
Pot B : 22 teams from Brazil, Colombia, Ecuador, Peru, and Venezuela
The 44 teams were drawn into 22 ties between a team from Pot A and a team from Pot B, with the teams from Pot B hosting the second leg in odd-numbered ties, and the teams from Pot A hosting the second leg in even-numbered ties. This distribution ensured that teams from the same association could not be drawn into the same tie.
Pot A
Pot B
;Notes
Format
In the first stage, each tie was played on a home-and-away two-legged basis. If tied on aggregate, the away goals rule would be used. If still tied, extra time would not be played, and the penalty shoot-out would be used to determine the winner. The 22 winners of the first stage advanced to the second stage to join the 10 teams transferred from the Copa Libertadores.
Matches
The first legs were played on 13, 15, 20–22 February, 10–12 and 18 April, and the second legs were played on 6–8 March, 8–10 and 23 May 2018.
Match E1
---- Tied 2–2 on aggregate, Caracas won on away goals and advanced to the second stage.
Match E2
---- Deportes Temuco won 3–1 on aggregate and advanced to the second stage.
Match E3
---- Lanús won 5–4 on aggregate and advanced to the second stage.
Match E4
---- Deportivo Cali won 5–3 on aggregate and advanced to the second stage.
Match E5
---- San Lorenzo won 1–0 on aggregate and advanced to the second stage.
Match E6
---- Tied 4–4 on aggregate, LDU Quito won on away goals and advanced to the second stage.
Match E7
---- Tied 0–0 on aggregate, Nacional won on penalties and advanced to the second stage.
Match E8
---- Cerro won 2–0 on aggregate and advanced to the second stage.
Match E9
---- Tied 3–3 on aggregate, Sol de América won on away goals and advanced to the second stage.
Match E10
---- General Díaz won 2–1 on aggregate and advanced to the second stage.
Match E11
---- Tied 2–2 on aggregate, Deportivo Cuenca won on penalties and advanced to the second stage.
Match E12
---- Rampla Juniors won 4–2 on aggregate and advanced to the second stage.
Match E13
---- Defensa y Justicia won 3–1 on aggregate and advanced to the second stage.
Match E14
---- Atlético Paranaense won 4–2 on aggregate and advanced to the second stage.
Match E15
---- Sport Huancayo won 3–0 on aggregate and advanced to the second stage.
Match E16
---- Boston River won 4–2 on aggregate and advanced to the second stage.
Match E17
---- São Paulo won 1–0 on aggregate and advanced to the second stage.
Match E18
---- El Nacional won 4–3 on aggregate and advanced to the second stage.
Match E19
---- Bahia won 4–1 on aggregate and advanced to the second stage.
Match E20
---- Colón won 3–0 on aggregate and advanced to the second stage.
Match E21
---- Botafogo won 3–2 on aggregate and advanced to the second stage.
Match E22
---- Fluminense won 3–2 on aggregate and advanced to the second stage.
