2017 Tercera División play-offs

The eighteen group winners have the opportunity to be promoted directly to Segunda División B.

The nine losing clubs will enter the play-off round for the last nine promotion spots.

The twenty-seven winners will advance with the nine losing clubs from the champions' series to determine the eighteen teams that will enter the last two-legged series for the last nine promotion spots.

In all the playoff series, the lower-ranked club play at home first.

Whenever there is a tie in position (e.g. like the group winners in the champions' series or the third-placed teams in the first round), a draw determines the club to play at home first.