[1] Quercus mulleri is currently known from a single small population in Miahuatlán District of southern Oaxaca.

Here it is found in montane conifer–oak forest on rugged terrain at approximately 1850 meters elevation.

[1] Quercus mulleri has a very low population and very limited range, and its conservation status is assessed Critically Endangered.

A recent genetic analysis suggests the species is a self-incompatible outbreeder, and may be a relict population from the Pleistocene.

Recent construction of a road to the species' remaining habitat is likely to increase human disturbance.