This medium-sized opossum is characterized by black rings around the eyes, white limbs, gray to light brown coat, lighter flanks and underbelly and a thick 12.7–14.6 centimetres (5.0–5.7 in) long tail covered with hairs.

[3][4] The cladogram below, based on a 2016 study, shows the phylogenetic relationships of the elegant fat-tailed mouse opossum.

[1] It lives in nests (abandoned by birds and rodents, or built by itself) in tree hollows, under rocks and roots.

[7] This opossum can use its prehensile tail, regardless of its thickness, to efficiently climb and grasp branches – an ability not as developed in other small Chilean mammals.

[10] Nests are generally occupied by one individual; in southern Chile, the home range of this opossum is 1,383 square metres (14,890 sq ft) large in July, and shrinks to 781 square metres (8,410 sq ft) in December.

[2] The elegant fat-tailed mouse opossum occurs in a variety of habitats – from cloud forests to chaparrals, up to an altitude of 2,500 metres (8,200 ft) above the sea level.

The IUCN lists this opossum as least concern given its wide distribution and presumably large numbers, but deforestation and agricultural expansion have led to decline in populations in some parts of the range.