The tail ranges from slightly shorter than the head and body to considerably longer. The pelage is long, soft, and thick. The upper parts are some shade of brown or buff, the sides are generally paler, and the underparts are grayish, buff, or fawn. In most species the scantily haired tail is darker above than below. The skull is elongate, the feet are long and narrow, and there are six plantar pads.
Females have two pairs of mammae.
Apomys is distinguished from Rattus and all other murid genera by a combination of features. The interorbital region of the skull is wide, and the margins of the interorbital and postorbital areas are rounded, without ridges or shelves. The braincase is smooth and globular, without the supraorbital ridges that extend back along the margins of the braincase, a characteristic of most species of Rattus. The squamosomastoid foramen is generally much more prominent in Apomys than in Rattus. In Apomys the bullae are small and loosely attached to the braincase.