A total of 16 teams competed in the final stages to decide the champions of the 2015 Copa Sudamericana.
The qualified teams were seeded in the final stages according to the draw of the tournament, which was held on July 16, 2015, 20:00 UTC−4, at the Salón Joao Havelange of the CONMEBOL Convention Centre in Luque, Paraguay, with each team assigned a "seed" 1–16 by draw.
Tied 0–0 on aggregate, Defensor Sporting won on penalties and advanced to the quarterfinals (Match S2).
Tied 2–2 on aggregate, Santa Fe won on away goals and advanced to the quarterfinals (Match S3).
The finals were played on a home-and-away two-legged basis, with the higher-seeded team hosting the second leg.