Head and body length is 110-14 mm and tail length is about 88 mm. The general color of the upper parts is dark slaty gray, which gradually blends into the lighter underparts, with no distinctive line of demarcation. The limbs are like the back in color, and the hands, feet, and tail are scantily covered with fine white hairs.
Fine scales are conspicuous on the tail.
The body is streamlined, the head is long and like that of Hydromys, the ears are short and round, the eyes are small, the tail is much shorter than the head and body, and the coat is water-resistant. Nonetheless, the feet are not webbed, and there is some question whether Xeromys is aquatic. There are only two molar teeth on each side of the skull. Females have four mammae. It is an agile climber and is well adapted to tidal areas.