The broad-toothed mouse reaches a weight of 150 grams and head and body length of 16 cm. It has a grizzled sandy brown to dark brown coat. It is similar in appearance to the swamp rat, which can also occur in similar habitat. The broad-toothed mouse is an uncommon resident of scrub and sedgeland, where it feeds on sedges, grasses and seeds. Although also occurring on mainland Australia, the species appears to be restricted to small areas where suitable habitat occurs.
Fossil evidence shows that the species was once more widely distributed on the mainland.
In Tasmania, the species occurs in the western half of the state. Breeding occurs from October to March, with up to two litters of 1-3 young per year. The young are weaned when about five weeks old. This common species occurs in a variety of habitats, ranging from wet and dry sclerophyll forests to buttongrass moorlands and coastal heath. It forms extensive systems of runways beneath dense vegetation.