A medium-sized shrew (adults usually 9 to 11 cm total length, tail 35 to 45 mm, 3 to 6 g) with a sharply pointed snout, beady eyes, and small ears nearly hidden in the fine soft pelage; dorsal pelage varies from dark brown to gray, depending on the season and location. Masked Shrews are most active after dark, when 85 per cent of activity occurs. They are especially active between 01:00 and 02:00, when there has been a rainfall, or on very dark nights. Their primary activity is hunting. Common shrews hunt primarily on the ground but may also climb into low vegetation and shrubs.

The live in a variety of habitat types, with a preference for moist woodland with leaf cover and logs. This carnivore primarily eats caterpillars, grubs, slugs, and spiders, using grassy and leafy cover to hunt prey. They run quickly, can jump to 10-15 cm high, and dig in loose soil. The masked shrew has the largest range of any North American shrew, and occurs throughout Alaska, Canada, the northern third of the U.S., as well as portions of the Great Basin, Rockies, and Appalachians. This shrew is found in all terrestrial habitats, natural or disturbed, from the lowest to highest elevations.