This 3-month-old child presented with an enlarging head circumference arising from communicating hydrocephalus with large subarachnoid spaces in the posterior fossa. Neuroimaging performed to clarify the origin and pathogenesis of the hydrocephalus revealed a vascular lesion within the dorsal spinal cord. Insertion of a cerebrospinal fluid shunt and total removal of the spinal tumor were performed successfully. Histological examination of the medullar lesion demonstrated a capillary hemangioma. Proposed mechanisms for increased intracranial pressure and spinal cord lesions are presented. A spinal hemangioma in this age range associated with hydrocephalus has not been reported previously, but spinal lesions must be considered in the presence of hydrocephalus with no clear origin.