An 11-yr-old, female Arizona ridge-nosed rattlesnake (Crotalus willardi) had a 1-yr history of retained egg masses and decreased mobility in the caudal two-thirds of the body. The snake was euthanized when it became unable to right itself. At necropsy, the caudal portion of the spinal cord was found to be enlarged, soft, and translucent pale gray. Microscopically, the caudal portion of the spinal cord was segmentally replaced by a neoplastic mass composed of cells resembling glia (oligodendrocytes and astrocytes). Immunohistochemistry for glial fibrillary acidic protein was positive in the astrocytelike neoplastic cells. The gross, microscopic, and immunohistochemical findings were consistent with a diagnosis of spinal cord glioma. This is the first report of a central nervous system tumor in a reptile.