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Mesenchymal chondrosarcoma (MCS) is a rare tumor in the orbit. Although optic nerve displacement is a common finding in intraorbital MCS, optic nerve tissue involvement in tumor has rarely been reported in huge tumors associated with intracranial extension. Herein the authors report a patient with MCS involving optic nerve tissue without intracranial extension. A 59-year-old woman with a 2-month history of progressive proptosis and normal vision presented to us. Computed tomography revealed a clearly outlined heterogeneous mass with calcified foci in its center, which was attached to the optic nerve, magnetic resonance imaging showed the mass to be isointense to gray matter on T1- and T2-weighted images. She underwent lateral orbitotomy and partial tumor excision. Histopathologic study confirmed MCS. She refused exenteration till 1 year but the tumor recurred and her vision decreased to no light perception. Then exenteration was performed with obtaining free margin and she is now free of tumor after 6 months without radiotherapy or chemotherapy. Mesenchymal chondrosarcoma must be differentiated from more common calcified tumors attached to optic nerve like meningioma.