Transverse testicular ectopia is an extremely rare anomaly, characterized by migration of one testis towards the opposite inguinal canal, usually associated with inguinal hernia. Spermatic cord of the ectopic testis originates from the appropriate side. In most reported cases, the accurate diagnosis has not been made before surgery. This is a case report of transverse testicular ectopia in eleven-year-old boy who had undergone an operation for the left inguinal hernia in age often months. At the time of herniorrhaphy, the right testis was absent. Ten years later, during re-operation of the left inguinal hernia, both testis were found in left inguinal canal and easily brought down sequentially through the left groin into the scrotum. The right testis was fixed in the left hemiscrotum, due to shorter funicular elements, and the left was trans-septally moved to the right hemiscrotum (a modified Ombrédanne operation). Ultrasonography and voiding cystoureterography showed no associated genitourinary anomalies and no Mülerian duct remnants. The rupture of gubernaculum and dysfunction of the genito-femoral nerve could explain the etiology of crossed testis ectopia. Although ectopic testis could be localized preoperatively by ultrasonography, CT, MRI, arteriography and venography, correct diagnosis was made intraoperatively in the majority of cases. Treatment modalities include laparoscopic and surgical procedures. Atrophie testis should be removed. If testes are fused, they have to be brought into one hemiscrotum. In cases where testes are completely separated with individual funicular elements and vas deferens, an ipsilateral or contralateral orchiopexy should be performed depending on the length of funicular elements.