Retroperitoneal schwannomas are rare, usually benign tumors that originate in the neural sheath and account for only a small percentage of retroperitoneal tumors. We report a case of a 34 year old male presented to our department complaining of left abdominal mass and pain. An abdominal computed tomography (CT) scan showed a large retroperitoneal mass of 15 cm in diameter. Histopathological examination confirmed the diagnosis of benign schwannoma. After two years, at follow-up the patient was free of disease. Retroperitoneal schwannoma is a difficult clinical diagnosis and requires a high index of suspicion. Magnetic resonance imaging scan may help in the diagnosis of schwannoma and diagnosis is based on histopathological examination and immunohistochemistry. Complete excision has a therapeutic effect and a good prognosis.