The 1985–86 Segunda División B season was the 9th since its establishment.
40 teams joined the league, including four relegated from the 1984–85 Segunda División and 6 promoted from the 1984–85 Tercera División.
The composition of the groups was determined by the Royal Spanish Football Federation, attending to geographical criteria.
Teams from Andorra, Aragon, Asturias, Basque Country, Castile and León, Catalonia and Galicia.
Teams from Andalusia, Balearic Islands, Castilla–La Mancha, Ceuta, Extremadura, Madrid, Region of Murcia and Valencian Community.