The aim of this study was to evaluate the utility of immediate repair of a contralateral occult hernia at the same time as incipient hernia repair. A total of 693 patients were diagnosed preoperatively with a unilateral groin hernia from January 2006 to December 2017. The open technique was used for 541 patients, and the laparo-endoscopic technique was used for 152 patients. The incidences of occult contralateral hernia confirmed during surgery under laparo-endoscopic techniques and those of contralateral metachronous hernia after a unilateral groin hernia repair with open technique were compared. Fifty-one (9.4%) of 541 patients underwent a contralateral metachronous hernia repair after unilateral groin hernia repair. Twenty-three (15.1%) of 152 patients had occult contralateral hernias using laparo-endoscopic techniques. There was a significant difference in the incidence of contralateral metachronous hernia and that of occult contralateral hernia (P = 0.02). It is concluded that finding and repairing an occult contralateral hernia at the time of laparo-endoscopic technique has the advantage of avoiding a second operation. However, it has been considered overtreatment to repair all patients with an occult contralateral hernia.