A diminutive shrew from Sioux County, Nebraska, is shown to be the first state record for the dwarf shrew, Sorex nanus. This specimen appears to be a member of a dwarf shrew population occurring on the Great Plains in the vicinity of the Black Hills in western South Dakota, eastern Wyoming, and southeastern Montana, but not within the Black Hills proper. Other populations of this species occur in montane environments in the Rocky Mountains, from Montana south through Wyoming, Colorado, New Mexico, Utah, and some isolated mountains in Arizona. The arid grassland habitats inhabited by the Great Plains population are strikingly different from the alpine and subalpine rockslides, coniferous forests, montane streams, and sagebrush communities at elevations generally above 1400 m occupied by other populations. Future researchers should examine genetic and ecological relationships among these populations of the dwarf shrew.