Monito del Monte is believed to be primarily arboreal, though it my take refuge underground when released from a trap. Nests are small round structures made of sticks, leaves, mosses and grasses and can occur under rocks, fallen trees, in tree hollows, on branches or suspended in lianas. The head and body length of Monito del Monte is 83-103mm, tail length is 90-132mm and weight is 16.7-31.4 grams. The fur is short, silky and dense. Upper parts are mostly brown with ashy white patches on the shoulders and rump. Underparts can be pale. The semi-prehensile tail is furred but for a narrow strip 25-30mm long on the underside of the tip.

Monito del Monte lives mostly in pairs, at least during mating season. Females have a small but distinct pouch and four mammae. Litters of one to five young have been observed and develop in four distinct stages: 1) in the pouch, attached to the mammae, 2) in the nest, 3) nocturnal trips on the mother's back, and 4) loose association with other family members. Both males and females mature sexually in their second year.

Almost entirely nocturnal, Monito del Monte feeds mainly on insects and other small invertebrates. In colder climates, Monito del Monte hibernates for lengthy periods when resources are scarce. Accumulation of fat in the basal part of the tail can more than double the weight of an individual in one week.

They are found in Chile and adjacent Argentina from about 36ºS to near 43ºS.