The head is nearly black. The arms and legs are grayish, and the hands and feet are brown, becoming white on the digits. Hexagonal scales show through the scantily haired tail. Anisomys has small ears, strong scansorial feet, and a long tail. The great toe has a broad nail.
Females have six mammae.
The lower incisor teeth are laterally compressed and bladelike and are less than half the width of the upper incisors. The molar teeth are remarkably small, the length of the toothrow in a given specimen being less than half that of a specimen of Uromys with the same external measurements. Most specimens have been trapped on the ground, but the broad scansorial feet indicate an ability to climb easily. The small size of the molars may be associated wth a diet that includes nuts with hard shells but soft, pulpy interiors.