Although endometriosis is a common disease in women of childbearing age, intestinal endometriosis is unusual and may cause clinically significant complications. We report a 46-year-old woman with rectal endometriosis who presented with intestinal obstruction. She was operated on with a preoperative diagnosis of malignancy. The diagnosis of endometriosis was made only after histological examination of the resected specimen. Intestinal endometriosis has a diverse clinical spectrum, with nonspecific features in many patients. In female patients who have unexplained digestive complaints, endometriosis should also be considered in the differential diagnosis.