The 1998–99 Argentine Primera B Nacional was the 13th season of second division professional of football in Argentina.
A total of 33 teams competed; the champion and runner-up were promoted to Argentine Primera División.
The winning team was declared champion and was automatically promoted to Primera División.
Teams placed 15th and 16th of the Relegation Table Interior Zone (Huracán Corrientes and Douglas Haig), played a promotion/relegation playoff or Torneo Reclasificatorio, with General Paz Juniors and Villa Mitre, teams from Torneo Argentino A.
Huracán Corrientes and Douglas Haig were relegated to Torneo Argentino A and General Paz Juniors stayed on it.