2018 Copa Sudamericana second stage
The 2018 Copa Sudamericana second stage was played from 17 July to 16 August 2018. A total of 32 teams competed in the second stage to decide the 16 places in the final stages of the 2018 Copa Sudamericana.
Draw
The draw for the second stage was held on 4 June 2018, 20:00 PYT, at the CONMEBOL Convention Centre in Luque, Paraguay. For the second stage, the teams were allocated to two pots according to their previous results in this season:
- Pot 1: 10 teams transferred from the Copa Libertadores and six best winners of the first stage from the Copa Sudamericana
- Pot 2: 16 remaining winners of the first stage from the Copa Sudamericana
The following were the 10 teams transferred from the Copa Libertadores.
| Match | Best teams eliminated in third stage | Second stage draw |
| G3 |  Jorge Wilstermann | Pot 1 |
| G2 |  Banfield | Pot 1 |
| Group | Third-placed teams in group stage | Second stage draw |
| A |  Defensor Sporting | Pot 1 |
| B | Bolívar | Pot 1 |
| C | Peñarol | Pot 1 |
| D |  Santa Fe | Pot 1 |
| E |  Vasco da Gama | Pot 1 |
| F | Nacional | Pot 1 |
| G | Millonarios | Pot 1 |
| H | Junior | Pot 1 |
The following were the 22 winners of the first stage from the Copa Sudamericana. Matches in the first stage were considered for the ranking of teams for the second stage draw.
Format
In the second 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 16 winners of the second stage advanced to the round of 16 of the knockout stages.
Matches
The first legs were played on 17–19, 25–26 July, and 1–2 August, and the second legs were played on 24, 31 July, 1–2, 7–9 and 14–16 August 2018.Match O1
----Millonarios won 5–1 on aggregate and advanced to the round of 16.
Match O2
----Botafogo won 3–2 on aggregate and advanced to the round of 16.
Match O3
----Nacional won 1–0 on aggregate and advanced to the round of 16.
Match O4
----Tied 1–1 on aggregate, Colón won on penalties and advanced to the round of 16.
Match O5
----Banfield won 2–1 on aggregate and advanced to the round of 16.
Match O6
----Fluminense won 3–0 on aggregate and advanced to the round of 16.
Match O7
----Atlético Paranaense won 6–1 on aggregate and advanced to the round of 16.
Match O8
----Deportivo Cali won 6–1 on aggregate and advanced to the round of 16.
Match O9
----LDU Quito won 3–2 on aggregate and advanced to the round of 16.
Match O10
----Caracas won 6–3 on aggregate and advanced to the round of 16.
Match O11
----Tied 4–4 on aggregate, Deportivo Cuenca won on penalties and advanced to the round of 16.
Match O12
----Defensa y Justicia won 2–1 on aggregate and advanced to the round of 16.
Match O13
----Tied 1–1 on aggregate, Junior won on penalties and advanced to the round of 16.
Match O14
----San Lorenzo won 3–1 on aggregate and advanced to the round of 16.
Match O15
----Bahia won 3–1 on aggregate and advanced to the round of 16.
Match O16
----Santa Fe won 2–0 on aggregate and advanced to the round of 16.