Nothofagus forest is generally found above a lower montane belt of oak relatives Castanopsis and Lithocarpus (family Fagaceae).

It grows with N. starkenborghiorum in montane forest around Lake Habbema in the Jayawijaya Range of Western New Guinea from about 2000 to 3000 meters elevation, and in upper montane mossy forest from approximately 3,000 to 3,500 meters elevation.

Since the 2000s it has been the target of massive illegal logging in parts of its range, including in Lorentz National Park.

[3] The Dani people of the Baliem Valley in western New Guinea use the leaves and bark of N. brassii and N. starkenborghiorum (both commonly known as sagé) to treat many chronic illnesses with symptoms resembling cancer and degenerative diseases.

Nothofagin is a dihydrochalcone, a phenolic antioxidant and C-linked phloretin glucoside, which may account for its efficacy in traditional medicine.