There were six participating teams in the Santam Bank Trophy Division B.
The top two teams in the division – along with the top two teams from Division A qualified for the title play-off finals.
The Division B champion qualified for the promotion play-offs.
The winner over these two ties qualified for the 1990 Santam Bank Trophy Division A, while the losing team qualified for the 1990 Santam Bank Trophy Division B.
In the promotion play-offs, South Western Districts beat Northern Natal on aggregate and won promotion to Division A.