Monodelphis kunsi is probably the smallest species in the genus Monodelphis. The mass of specimens lies between 7.5 and 30 grams and length between 103 and 147 millimiters. Monodelphis kunsi lacks a sagittal crest on the skull and enlarged canines. Unlike M. americana and M. brevicaudata, pygmy short-tailed opossums have no dorsal stripes or lateral reddening. M. kunsi have throat glands covered by thin fur. Over the body, the fur of these opossums is short, generally warm brown on the dorsal side and with whitish areas on the ventral side. The tail is bicolored, darker dorsally and buffy ventrally; covered by fine hair, except for the tip which may serve a tactile function. The skull is small (about 22 mm in length) with no postorbital processes and a relatively blunt rostrum. The head is covered with numerous mystacial, genal, supraorbital, and interramal vibrissae. The hind feet have noticeable webs between digits 3 and 4 and a less conspicuous web between digits 2 and 3. All members of the genus Monodelphis lack abdominal pouches.
Range mass: 7.5 to 30 g.
Range length: 103 to 147 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike