Idiopathic colonic perforation in adults is rare. We report a case of idiopathic sigmoid colon perforation in an adult male who presented to the emergency room with signs and symptoms of perforation peritonitis. On exploratory laparotomy, a single perforation was found on the antimesenteric border of the sigmoid colon, the biopsy of which revealed non specific acute inflammation. On evaluation, no etiological factor was found for the perforation.