Although this animal is referred to as a "rat" it is more mouse-like in appearance and has a bicolor tail and also has larger ears and eyes, a larger, heavier head, and much longer whiskers. It is gray above with white underparts and paws. The average adult weighs less than a pound and is about 17 inches in total length, including an eight-inch tail. They are largely solitary, tolerating each other during the breeding season. Common predators of the Allegheny woodrat include great horned owls, black rat snakes, raccoons, and coyotes. They have large eyes, and naked ears.

Individual woodrats build a nest of plant material within a rock outcrop and may surround the nest with dry leaves and twigs, possibly as an alarm system. They emerge at dusk to forage for food, which includes a variety of leaves, fruit, nuts, seeds, fungi and twigs. Ideal habitat for woodrats are surface rock surrounded by a forest. Muntain ridges such as cliffs, caves, talus slopes, and even mines are preferred, providing protection and locations for nests and food caches. This is mostly true for Pennsylvania and Maryland. In Virginia and West Virginia, woodrats are found on ridges, but also on side slopes boulders and breakdown fields.