Optic pathway oligodendrogliomas are a rare form of pediatric intracranial tumor. A 10-year-old girl presented with symptoms of hydrocephalus and seizure. Head computed tomography and magnetic resonance images showed hydrocephalus, chiasmal tumor, and enlarged and tortuous optic nerves. The tumor was partially removed by operation and diagnosed as oligodendroglioma. Operatively, there was evidence of cerebrospinal fluid dissemination in the sylvian fissure indicating widespread invasion. After the operation, Packer's regimen (vincristine and carboplatin therapy) was administered. However, magnetic resonance images obtained 2 months after the operation revealed enlargement of the original tumor and the appearance of new lesions, and treatment was changed to irradiation and temozolomide therapy according to the presence of a high-grade glioma. Two years after the operation, the patient is free of neurological symptoms, and the tumor is controlled with partial response. This is the first report of pediatric optic pathway oligodendroglioma presenting widespread invasion and cerebrospinal dissemination.