We present a case of perforated giant diverticulum of the sigmoid colon. This condition is extremely rare and only a few cases have so far been reported in the literature. Our case involved a 55-year old woman. Diagnosis was easy with barium enema and CT scan examination. Laparotomy revealed a giant diverticulum of the sigmoid colon compressing adjacent structures with signs of inflammation. An en bloc resection of the sigmoid colon, ovary and fallopian tube was performed with primary colon-rectal anastomosis. The post-operative course was uneventful.