Colonoscopy is generally considered a safe procedure, with a low rate of complications. Although rare, the migration of the colonoscope may represents a life-threating events, requiring emergency treatment. We herein describe the case of an elective colonoscopy complicated by an irretrievable colonoscope that migrated, through a previous traumatic diaphragmatic hernia, in the chest cavity. This hernia was likely a chronic complication of a previous abdominal trauma. Several attempts to retrieve the scope were unsuccessful. After further investigations and collegial discussion, a left thoracotomy was performed, with the aim to retrieve the colonoscope and to reduce the hernia.