Fourteen teams participated in the 1990–91 Cypriot Second Division.
The team with the most points at the end of the season crowned champions.
Enosis Neon Paralimni won both matches and secured their place in the 1991–92 Cypriot First Division.
The 12th-placed team, Ermis Aradippou, faced the 3rd-placed team of the 1990–91 Cypriot Third Division, Apollon Lympion, in a two-legged relegation play-off for one spot in the 1991–92 Cypriot Second Division.
Apollon Lympion won the playoff and secured their place in the 1991–92 Cypriot Second Division.