A case of gliosarcoma composed of glioblastoma and liposarcoma is presented. A 70-year-old Japanese man was admitted to hospital because of dysarthria and aphasia. Magnetic resonance imaging indicated a brain tumor located in the temporal–parietal area of the left hemisphere. He rejected any therapy and died of respiratory failure. At autopsy the tumor was well-demarcated with firm consistency and myxoid appearance, accompanied by necrosis and hemorrhage. Microscopically the tumor consisted of both glial and sarcomatous components, compatible with a gliosarcoma. Lipoblast-like tumor cells were identified in the sarcomatous area. Glial component was observed in the periphery and was diffusely positive for CD56 and S100 protein and focally for glial fibrillary acidic protein. Only a small number of tumor cells in the sarcomatous area expressed neurogenic markers. Lipoblast-like tumor cells were positive for S100 protein but negative for any other neurogenic markers. A significant number of tumor cells were positive for retinoblastoma protein (pRB) in the glial area, whereas only a few of them were positive in the sarcomatous area, indicating alteration of pRB in sarcomatous component. The present tumor is a rare gliosarcoma with liposarcomatous differentiation; alteration of pRB may play a role in sarcomatous transformation of glial component.