See-saw nystagmus has been seen with tumors of the parasellar region and diencephalon, brain-stem vascular lesions, syringobulbia, and after trauma. We report see-saw nystagmus in an adult with a Chiari malformation that was diagnosed by magnetic resonance imaging and confirmed intraoperatively. This patient's condition improved after surgical decompression. An association between see-saw nystagmus and Chiari malformation is potentially important because early diagnosis and decompression may improve neurologic function and prevent further deterioration.