Within each group, the teams would play a double round-robin to decide their league position.
The four group winners and the four runners-up then contested a play-off for the three promotion slots.
The four third-last placed teams would compete a play-out against the ninth relegation spot.
FC Thun win 3–1 on aggregate and continue to the finals.
[8] The play-off for the third promotion place was played on 24 June 1989 in Burgdorf.
FC Brüttisellen win after penalty shoot-out and are promoted to 1989–90 Nationalliga B[8] The play-off for the championship place was played on 24 June 1989.