Isolated involvement of the optic nerve with metastatic tumor is uncommon. A 19-year-old man had a midline cerebellar medulloblastoma; a gross total removal was performed. He received postoperative radiation therapy to the whole brain, posterior fossa, and craniospinal axis. A progressive optic neuropathy developed 28 months later with radiologic evidence of an enlarged optic nerve. There was no evidence of metastatic disease elsewhere. An optic nerve biopsy showed metastatic medulloblastoma. An intramedullary metastasis developed 48 months after the primary diagnosis, and the patient died 5 months later.