The 2018 Copa Sudamericana final stages were played from 21 August to 12 December 2018.[1] A total of 16 teams competed in the final stages to decide the champions of the 2018 Copa Sudamericana.[2]
The 16 winners of the second stage advanced to the round of 16.
Starting from the round of 16, the teams were seeded according to the second stage draw, with each team assigned a "seed" 1–16 corresponding to the tie they win (O1–O16) (Regulations Article 22.c).[2]
| Seed | Match | Second stage winners | |
|---|---|---|---|
| 1 | O1 |  Millonarios | |
| 2 | O2 |  Botafogo | |
| 3 | O3 | Nacional | |
| 4 | O4 |  Colón | |
| 5 | O5 | Banfield | |
| 6 | O6 | Fluminense | |
| 7 | O7 | Atlético Paranaense | |
| 8 | O8 | Deportivo Cali | |
| 9 | O9 |  LDU Quito | |
| 10 | O10 |  Caracas | |
| 11 | O11 | Deportivo Cuenca | |
| 12 | O12 | Defensa y Justicia | |
| 13 | O13 | Junior | |
| 14 | O14 | San Lorenzo | |
| 15 | O15 | Bahia | |
| 16 | O16 | Santa Fe |
Starting from the round of 16, the teams played a single-elimination tournament with the following rules:[2]
The bracket starting from the round of 16 was determined as follows:
| Round | Matchups | |
|---|---|---|
| Round of 16 | (Higher-seeded team host second leg)
| |
| Quarterfinals | (Higher-seeded team host second leg)
| |
| Semifinals | (Higher-seeded team host second leg)
| |
| Finals | (Higher-seeded team host second leg)
|
The first legs were played on 21–22 August, 18–20 and 26 September, and the second legs were played on 19, 25, 27 September, and 2–4 October 2018.[3] [4] |}
----Tied 0–0 on aggregate, Santa Fe won on penalties and advanced to the quarterfinals (Match S1).
----Tied 3–3 on aggregate, Bahia won on penalties and advanced to the quarterfinals (Match S2).
----Tied 3–3 on aggregate, Nacional won on away goals and advanced to the quarterfinals (Match S3).
----Junior won 2–1 on aggregate and advanced to the quarterfinals (Match S4).
----Defensa y Justicia won 2–0 on aggregate and advanced to the quarterfinals (Match S4).
----Fluminense won 4–0 on aggregate and advanced to the quarterfinals (Match S3).
----Atlético Paranaense won 4–1 on aggregate and advanced to the quarterfinals (Match S2).
----Tied 1–1 on aggregate, Deportivo Cali won on penalties and advanced to the quarterfinals (Match S1).
The first legs were played on 23–25 October, and the second legs were played on 30–31 October and 1 November 2018.[5] [6] |}
----Santa Fe won 3–2 on aggregate and advanced to the semifinals (Match F1).
----Tied 1–1 on aggregate, Atlético Paranaense won on penalties and advanced to the semifinals (Match F2).
----Fluminense won 2–1 on aggregate and advanced to the semifinals (Match F2).
----Tied 3–3 on aggregate, Junior won on away goals and advanced to the semifinals (Match F1).
The first legs were played on 7–8 November, and the second legs were played on 28–29 November 2018.[7] [8] |}
----Junior won 3–0 on aggregate and advanced to the finals.
----Atlético Paranaense won 4–0 on aggregate and advanced to the finals.
See main article: article and 2018 Copa Sudamericana Finals.
In the finals, if tied on aggregate, the away goals rule would not be used, and 30 minutes of extra time would be played. If still tied after extra time, the penalty shoot-out would be used to determine the winner (Regulations Article 28).[2]
The first leg was played on 5 December, and the second leg was played on 12 December 2018.----Tied 2–2 on aggregate, Atlético Paranaense won on penalties.