The montane oldfield mouse occurs in the Andes from northern Peru to central Bolivia. It is recorded in high-montane forests, often in trees, though ground records also exist.
The handbook describes a soft Prout-brown to darker back, a pale pinkish-buff underside and a tail longer than the head and body.
Seeds and arthropods are reported in its diet. It is often recorded in trees, although ground records also exist.
An extinction-risk assessment has not been added yet.