The 1989–90 Argentine Primera B Nacional was the fourth season of second division professional of football in Argentina.
A total of 22 teams competed; the champion and runner-up were promoted to Argentine Primera División.
The Second Promotion Playoff or Torneo Reducido was played by the teams placed 2nd to 10th in the overall standings: Quilmes (2nd) who entered in the Semifinals, Douglas Haig (3rd) who entered in the Second Round, San Martín (T) (4th), Lanús (5th), Atlético de Rafaela (6th), Belgrano (7th), Banfield (8th), Sportivo Italiano (9th) and Colón (10th); the champion of Primera B Metropolitana: Deportivo Morón and Deportivo Laferrere and Atlanta, both winners of Zonales Noroeste y Sureste from Torneo del Interior.
Note: As the series ended 2–2 on aggregate (extra time included), Lanús won 4–1 on penalties, promoting to Primera División Note: Clubs with indirect affiliation with AFA are relegated to their respective league of his province according to the Argentine football league system, while clubs directly affiliated face relegation to Primera B Metropolitana.
This season, Cipolletti had to play against Fernández Oro from the Liga Deportiva Confluencia (Río Negro Province), Central Córdoba (SdE) had to play against Güemes (SdE) from the Liga Santiagueña de Fútbol, and Atlético Tucumán had to play against Atlético Concepción from the Liga Tucumana de Fútbol.