To date, only 12 cases of mature cystic teratoma with sigmoid colon perforation have been reported in the literature.We report a rare case of mature cystic teratoma accompanied by sigmoid colon perforation treated using laparoscopicassisted surgery. A 25-year-old woman (gravida 2 para 0) was admitted to our hospital for evaluation of a 2-week history of fever. Magnetic resonance imaging revealed a large cyst filled with fat, as well as free air in the pelvis. Laboratory investigations showed evidence of significant inflammation. Therefore, we suspected mature cystic teratoma concomitant with bowel perforation.Colonoscopy confirmed a sigmoid colon perforation, and we performed laparoscopic-assisted surgery.Histopathological evaluation confirmed diagnosis of a mature cystic teratoma without malignant transformation.Malignancy should be considered in the differential diagnosis, and an appropriate operative procedure should be selected in patients with ovarian cysts concomitant with bowel perforation.