The underparts are white with a creamy wash. The upper sides of the feet are whitish with a buffy wash, or with tawny tones, and the tail is uniformly brown and heavily haired. The external ear is similar to that of Nyctomys. This rodent is much redder than Nyctomys sumichrasti, its pronounced russet coloration making it the showiest among the neotropical climbing rats. It resembles Nyctomys in structural features, but its auditory bullae are much larger, its cheek teeth are smaller, and its tarsus is narrower.
Females have four mammae.
In both instances the traps were baited with bananas. Robert T. Hatt trapped two individuals in a thatched hut, on the shelf where the rafters meet the top of the wall. The habits of Otonyctomys are probably much like those of Nyctomys and Rhipidomys. It is possible that Otonyctomys is fairly common and only seems to be rare because of its arboreal habits or because it may have a specialized diet. The Johns Hopkins University Press.