Mesenchymal chondrosarcoma is a rare malignant tumor of the orbit capable of mimicking several other lesions. Early diagnosis requires a high level of suspicion, particularly with regard to internally calcified lesions. The treatment of choice is complete surgical resection, or, when the tumor is not resectable or residual mass is present after surgery, chemotherapy and radiotherapy. Prognosis for patients with orbital mesenchymal chondrosarcoma is tentative at best, in part because of the rarity of the lesion.