The northern bog lemming is a small mammal about the size of a vole (about one ounce). The bog lemming has a blunt nose, short tail, and somewhat grayer coat than the common red-backed vole. The upper parts are dull brown, and are slightly brighter on the rump. Toward the head the fur has a grizzled appearance. Northern bog lemmings are social animals that live in colonies. Foods include sedges, grasses, raspberry seeds, and the fungus. Predators may include mammals, hawks, owls, and snakes. The ears extend noticeably beyond the body fur and are sparsely haired on the edge. The tail is extremely short. There are 16 teeth in the skull.

The northern bog lemming usually occurs in moist, wet meadows or boggy areas, often in conjunction with arctic or alpine tundra and spruce-fir forests. Frequently it occurs near a spring or other source of water or near lush, mossy logs and rocks. The northern bog lemming builds paths above ground or below the leaf litter. The nest is located either above ground concealed in vegetation, or several inches below ground. It is lined with dried leaves and grasses, and occasionally fur. Frequently it occurs near a spring or other source of water or near lush, mossy logs and rocks.