The 1986–87 ACB season was the 4th season of the ACB Primera División, the top Spanish professional basketball league.
It started on 13 September 1986 with the first round of the regular season and ended on 25 April 1987 with the finals.
Starting from this season, the promotions and relegations teams at the end of the season between ACB Primera División and Primera División B were reduced from three to two teams.
For the championship playoffs, the semifinals and finals adopted the best-of-five playoff, instead of previous season's best-of-three playoff that were kept for the first round and quarterfinals.
A total of 16 teams contested the league, including 13 sides from the 1985–86 season and three promoted from the 1985–86 Primera División B.