Gliosarcoma is a rare primary central nervous system tumor with a biphasic tissue pattern, displaying glial and mesenchymal differentiation. So far, there is only one description of an optic nerve gliosarcoma. We describe the case of a 66 years old patient who developed left eye pain that evolved to visual deficit and papilledema. The cerebral MRI showed a contrast enhancement of the left optic nerve in T1 weighted images. We performed an open biopsy that revealed a gliosarcoma. Keywords: Gliosarcoma, Glioblastoma, Optic pathway