[2] It was designated as a Class 1 Protection Forest by the Sabah Forestry Department in 1984.

[3] The reserve is hilly, with the highest point being Mount Mabauk at 836 metres (2,743 ft).

Two forest types make up the reserve: dipterocarp and kerangas.

Other species include Barringtonia sarcostachys, Carallia borneensis, Castanopsis motleyana, Irvingia malayana, Lithocarpus gracilis, Mangifera pajang and Octomeles sumatrana.

[1] Mandamai Forest Reserve is home to animals including barking deer and wild boar.