The 1988–89 Segunda División B season was the 12th since its establishment. The first matches of the season were played on 3 September 1988, and the season ended in 25 June 1989.
80 teams joined the league, including four relegated from the 1987–88 Segunda División and 17 promoted from the 1987–88 Tercera División. The composition of the groups was determined by the Royal Spanish Football Federation, attending to geographical criteria.
Teams from Asturias, Basque Country, Cantabria, Castile and Leon and Galicia.
Teams from Andorra, Aragon, Basque Country, Balearic Islands, Catalonia, La Rioja and Navarre.
Teams from Andalusia, Canary Islands, Castile and Leon, Castilla–La Mancha, Extremadura and Madrid.
Teams from Andalusia, Castilla–La Mancha, Ceuta, Melilla, Region of Murcia and Valencian Community.