Junior were the defending champions, but were knocked out by Atlético Nacional in the quarterfinals.
Atlético Nacional were the champions after beating Once Caldas 4–3 on aggregate in the final, and qualified for the 2019 Copa Libertadores.
Finally, in the round of 16, the eight third stage winners were joined by the four Copa Libertadores qualifiers (Atlético Nacional, Junior, Millonarios and Santa Fe), as well as the four Copa Sudamericana qualifiers (Independiente Medellín, América de Cali, Deportivo Cali, and Jaguares), which entered the competition at this point.
[1] The first stage was played by the 16 Categoría Primera B clubs, eight of which were seeded in the ties according to their position in the 2017 season aggregate table.
The four second stage winners as well as the best four teams according to the 2017 Primera A aggregate table hosted the second leg.
Each tie in the final stages will be played in a home-and-away two-legged format.