Schwannomas arise from cells that are found in neuron sheats and can be seen anywhere in the peripheral, cranial or sympathetic neurons. Schwannomas are usually seen at 20-50 years of age having an equal prevalence in both sexes and only 5% of them diagnosed in postmenopausal women. Five to eight percent of cases are associated with von Recklinghausen Syndrome. Retroperitoneal pelvic settlement of this type of tumor is an extremely rare occasion. This type of settlement can imitate an adnexal mass. Preoperative diagnosis of retroperitoneal schwannomas is difficult and usually incidental. Although recent imaging methods can define the settlement of the tumor they are not able to diagnose the nature of the lesion. Material obtained from the guided biopsies of the lesion may also reveal misleading histopathologic results. An accurate diagnosis may only be reached by the total excision and histopathologic examination of the tumor. Malignant degeneration and recurrence in schwannomas are extremely rare. Total excision is the treatment of choice. Chemotherapy and radiotherapy are not considered as a choice of treatment. Malignant lesions must be considered priorly on the way to the diagnosis of postmenopausal adnexal mass lesions. Laparotomy and laparoscopy must be used for the clinical evaluation of these cases. In this report we presented a retroperitoneal pelvic schwannoma of 4 cm mimicking right adnexal mass which was found during routine pelvic examination of a 65-years-old asymptomatic postmenopausal woman.