Castanopsis microphylla is an evergreen tree that grows up to 30 m tall and 60 cm bole diameter. It is known as Kogopon in Dusun ethnic. Bark and twigs are smooth but sometimes the bark can be flaky. It has yellowish sapwood. The leaves have smooth surface and are sparsely tomentose below. They have leather-like texture and the shape varies from linear to lanceolate. Male flowers are grouped in clusters of 3-4 along the rachis while female flowers are grouped in clusters of 2-3 along the rachis. The perianth lobes of both male and female flowers are acute. Each asymmetrical cupule contains 2-3 equally developed ovoid seeds with a thin wall (Soepadmo & Saw, 2000).

At altitudes of up to 1600 m, Castanopsis microphylla can be found in lowland mixed dipterocarp forest to lower montane forest. This species is endemic to Borneo. In Sabah, it is reported from Ranau, Beaufort and Kinabatangan districts. In Sarawak, it is present in Kapit, Kuching, Mukah and Tatau districts (Soepadmo & Saw, 2000).