Leiomyosarcoma is usually found in the female genital tract, the retroperitoneum, the wall of the gastrointestinal tract, and subcutaneous tissues. An appearance of this malignant tumor in the parapharyngeal space is extremely rare and may be difficult to diagnose. Because of its rarity, little information exists on management and prognosis. We report the case of a 50-year-old man with a parapharyngeal space leiomyosarcoma who was treated with total excision of the tumor and postoperative radiotherapy. At follow-up 6 months postoperatively, he was well and free of disease. To the best of our knowledge, this is only the third case of a leiomyosarcoma in the parapharyngeal area to be reported in the literature. We discuss the diagnosis and treatment of leiomyosarcoma in this aspect.