A 38-year-old woman was referred to our hospital with a complaint of left buttock pain. Contrast-enhanced computed tomography and magnetic resonance imaging showed a 7cm smooth mass on the anterior sacrum adjacent to the small intestine and mesentery. The mass was suspected to be a gastrointestinal stromal tumor of the small intestine;however, a definitive diagnosis from radiological and clinical findings was impossible. Laparoscopic visualization revealed that there was no lesion in the small intestine;the mass situated in the retroperitoneally, in contact with the anterior sacrum around the aortic bifurcation. With a diagnosis of retroperitoneal tumor, laparoscopic resection was performed simultaneously. An incision was made in sigmoid mesentery, and the tumor was detached and resected preserving the anterior fascia of the hypogastric nerve. Intraoperatively the surface of the tumor was confirmed to be smooth, and there was no infiltration around the tumor, which facilitated handling and manipulation of the tumor for resection. The patient was discharged without any complications and the pathological diagnosis was benign schwannoma. Anterior sacral retroperitoneal schwannomas are rare and difficult to diagnose preoperatively. In this case, successfully management was achieved via simultaneous laparoscopic observation and resection.