Colo-Colo won their thirty-second title following a 3–0 away win at Huachipato on 9 December.
In order to manage this transition, the 2017 Clausura tournament, part of the 2016–17 season, was followed up by a single championship in the second semester of the year.
The Copa Sudamericana berth would then be awarded to the 2017 Transición best team not already qualified.
Relegation is determined at the end of the season by computing an average of the number of points earned per game over the three most recent tournaments: 2016 Apertura, 2017 Clausura and 2017 Transición.
The relegation playoff was played by three teams: the last-placed in the relegation table (Santiago Wanderers), 2016–17 Primera B runners-up San Marcos de Arica, and 2017 Primera B champions Unión La Calera.