Undifferentiated pleomorphic sarcoma (UPS) is an extremely rare tumor that occurs in the head and neck region. Here, we report a unique case of a primary undifferentiated pleomorphic sarcoma in the orbital region. A 35-year-old woman presented with a progressive proptosis and periocular edema for 1 year. She had no previous history of surgery, skin malignancy, or radiation. Imaging tests showed an extraconal mass, not involving the muscles. The tumor was surgically removed and adjuvant radiotherapy was required after histological examination, which showed an undifferentiated pleomorphic sarcoma of the orbit. There was no recurrence after 1 year of follow-up. Though rare, undifferentiated pleomorphic sarcoma should be included in the differential diagnoses of orbital tumors.