A 54-year-old man presented with a painful left proptosis and a soft tissue mass at the inferolateral aspect of the left orbit with bone involvement. There was no clinical or investigational evidence of systemic disease. Both light microscopy and immunohistochemistry were required for the diagnosis of Ewing sarcoma. After failure of chemotherapy alone, management included extensive surgical excision and postoperative adjuvant radiotherapy and chemotherapy. Despite intervention, the patient died of widespread metastatic disease 17 months after initial presentation. Although rare, Ewing sarcoma should be included in the differential diagnosis of uniform round cell orbital tumors in adults.