CASE DESCRIPTION A 3-year-old 31.1-kg castrated male mixed-breed dog was evaluated because of a 1- to 2-week history of paraparesis, knuckling of the hind feet, and difficulty posturing to urinate or defecate. CLINICAL FINDINGS The dog was paraparetic but weakly ambulatory with a kyphotic posture, a mildly decreased patellar reflex in the right pelvic limb, increased tone in both pelvic limbs, and marked hyperesthesia on paraspinal palpation of the lumbar region. The urinary bladder was enlarged and firm on palpation. Neuroanatomic findings were primarily consistent with localization to the T3-L3 spinal cord segments. Magenetic resonance imaging of the thoracolumbar spinal column revealed a discrete intramedullary spinal cord mass from the cranial aspect of L4 to the middle of L5. The mass was sampled by fine-needle aspiration, and on cytologic evaluation, the suspected diagnosis was an ependymoma. TREATMENT AND OUTCOME Owing to poor prognosis and limited treatment options, the owner elected euthanasia. Postmortem examination of the spinal cord and histologic findings for samples of the mass supported a likely diagnosis of ependymoma. CLINICAL RELEVANCE Ependymoma is a rare neoplasm in dogs but should be considered in young patients with evidence of a tumor in the CNS. Fine-needle aspiration of the spinal cord mass was possible in the dog of this report, and the cytologic findings provided useful diagnostic information.