We present a case with a nontraumatic subperiosteal orbital hematoma as a presenting sign of chronic myelogenous leukemia. A previously healthy 34 year-old man presented with a 2-day history of right upper eyelid swelling. CT scan revealed a subperiosteal mass, and routine blood tests revealed a white blood cell count of 290,000/μl with normal platelet count. Chronic myelogenous leukemia was diagnosed based on a subsequent bone marrow biopsy. After orbitotomy and evacuation of the hematoma, the patient's visual acuity and motility returned to normal. In conclusion, chronic myelogenous leukemia should be considered in the differential diagnosis of nontraumatic subperiosteal orbital hematoma.