Neurological deficits are a frequent complication of adult cardiac surgery. Dandy-Walker malformation (DWM) is a rare posterior fossa malformation defined by hypoplasia and upward rotation of the cerebellar vermis, cystic dilation of the fourth ventricle and, on occasion, hydrocephalus. We report an incidental diagnosis of DWM in an adult following coronary artery surgery complicated by delayed awakening.