Hereditary polioencephalomyelopathy was suspected in a young, female Australian Cattle Dog on the basis of clinical signs, including seizures, progressive ataxia, and weakness. Magnetic resonance imaging (MRI) of the brain revealed multiple ovoid, bilaterally symmetric signal abnormalities that were hypointense or isointense on T1-weighted images and hyperintense on T2-weighted images. On necropsy, these areas of signal abnormalities corresponded to areas of malacia in various brain and brain stem nuclei. In addition, poliomalacia was detected at the cervical intumescence of the spinal cord. Histologic examination revealed rarefaction of neuropil and vacuolation of glial cells in these areas, which are lesions consistent with hereditary polioencephalomyelopathy of Australian Cattle Dogs.