Until recently the Brown Mouse Lemur was distributed throughout the eastern rainforest from north to south. Recent research has identified several species within this complex to leave the Rufous Mouse Lemur restricted to a small area of montane forest around Ranomafana Park. See the distribution map at IUCN.

The head and forelegs are rufous while the back and tail are greyish-brown. Underparts are greyish-white while the ears are naked but much shorter than most other mouse lemurs.