The 2005 Segunda División B play-offs (Playoffs de Ascenso or Promoción de Ascenso) were the final playoffs for promotion from 2004–05 Segunda División B to the 2005–06 Segunda División.
The four first placed teams in each of the four Segunda División B groups played the Playoffs de Ascenso and the four last placed teams in Segunda División were relegated to Segunda División B.
Home Matches: Away Matches: Group A--Second Eliminatory Promoted to Segunda División: Hércules CF Group B--Second Eliminatory Promoted to Segunda División: CD Castellón Group C--Second Eliminatory Promoted to Segunda División: Lorca Deportiva CF Group D--Second Eliminatory Promoted to Segunda División: Real Madrid B