Leiomyosarcomas are rare smooth muscle tumors that can occur anywhere in the body. These tumors rarely occur in the head and neck owing to the limited amount of smooth muscle in the region. The clinical diagnosis of leiomyosarcoma is challenging because of the nonspecific presentation of the disease. The most definitive diagnosis is based on tissue biopsy or surgical resection and histopathologic confirmation. A case of intraosseous leiomyosarcoma of the mandible and a review of the literature are presented.