The 2018 Copa Sudamericana second stage is scheduled to be played from 17 July to 16 August 2018. A total of 32 teams compete in the second stage to decide the 16 places in the final stages of the 2018 Copa Sudamericana.
The draw for the second stage will be held on 2 June 2018 at the CONMEBOL Convention Centre in Luque, Paraguay. For the second stage, the teams are allocated to two pots according to their previous results in this season:
The 32 teams are drawn into 16 ties (O1–O16) between a team from Pot 1 and a team from Pot 2, with the teams from Pot 1 hosting the second leg. Teams from the same association can be drawn into the same tie.
The following are the 10 teams transferred from the Copa Libertadores (two best teams eliminated in the third stage of qualifying and eight third-placed teams in the group stage).
The following are the 22 winners of the first stage from the Copa Sudamericana. Matches in the first stage are considered for the ranking of teams for the second stage draw.
In the second stage, each tie is played on a home-and-away two-legged basis. If tied on aggregate, the away goals rule is used. If still tied, extra time is not played, and the penalty shoot-out is used to determine the winner (Regulations Article 27).
The 16 winners of the second stage advance to the round of 16 of the knockout stages.