A 29-year-old woman presented with a severe headache. Computed tomography revealed a large cystic lesion with a mural nodule-like mass homogeneously enhanced with contrast medium in the right cerebellum. The tumor was removed, and pathological studies revealed a cerebellar astrocytoma corresponding to World Health Organization grade II. When she was 35 years old, or 6 years after the surgery, magnetic resonance imaging revealed a recurrence of the tumor in the right cerebellum, and subtotal removal of the recurrent tumor was performed. Pathological studies revealed a mixed glioblastoma multiforme and anaplastic ependymoma. Chemotherapy (Paraplatin and VePeside-S) and focal radiation therapy at 60 Gy were administered following surgery. Thereafter, at 39 years of age, or 4 years after radiation therapy, magnetic resonance imaging again revealed a recurrence of the tumor, which was heterogeneously enhanced with gadoliniumdiethylenetriamine pentaacetic acid in the right cerebellum. Subtotal removal of the tumor was performed; pathological studies revealed an anaplastic ependymoma with sarcomatous components. Immunohistochemical findings showed some parts of the sarcomatous components to stain positively for glial fibrillary acidic protein and, as a result, these sarcomatous components were diagnosed to be gliosarcoma.