Synovial sarcoma is a high-grade soft tissue sarcoma, divided histologically into 3 types: Monophasic, biphasic and poorly differentiated. An extremely rare case of obstructive ileus due to monophasic synovial sarcoma in a 54-year-old male patient is reported in the present study. The patient presented to the emergency department with signs and symptoms of obstructive ileus. Computer Tomography (CT)scan showed a pelvic mass (20×17×12 cm) causing obstruction at the sigmoid colon. An exploratory laparotomy through a midline incision was performed. The described mass was unresectable as it was infiltrating major vessels. Therefore, a diverting loop descending colostomy and biopsy of the solid mass were performed. Pathological examination revealed a monophasic synovial sarcoma. The patient was referred to the Department of Oncology and started treatment with doxorubicin and ifosfamide.