The 2019 Segunda División B play-offs (Playoffs de Ascenso or Promoción de Ascenso) are the final playoffs for promotion from 2018–19 Segunda División B to the 2019–20 Segunda División. The four first placed teams in each one of the four qualify for the promotion playoffs and the four last placed teams in Segunda División are relegated to Segunda División B. It also decides the teams which placed 16th to be relegated to the 2019–20 Tercera División.
The four group winners have the opportunity to promote directly and become the overall Segunda División B champion. The four group winners will be drawn into a two-legged series where the two winners will be promoted to the Segunda División and will enter into the final for the Segunda División B champion. The two losing semifinalists will enter the playoff round for the last two promotion spots.
The four group runners-up will be drawn against one of the three fourth-placed teams outside their group while the four third-placed teams will be drawn against each other in a two-legged series. The six winners will advance with the two losing semifinalists to determine the four teams that will enter the last two-legged series for the last two promotion spots. In all the playoff series, the lower-ranked club will play at home first. Whenever there is a tie in position (e.g. like the group winners in the Semifinal Round and Final or the third-placed teams in the first round), a draw will determine the club to play at home first.
^Mirandés and UD Logroñés have assured at least the third place of their group, but either of them may still reach the second place of the group.
^Atlético Baleares has assured at least the 3rd place of their group, but may still win the group and qualify for the correspondent play-off.
^Cartagena, Melilla and Recreativo has assured at least the third place of their group, but may still win the group and qualify for the correspondent play-off.
