Transverse testicular ectopia (TTE) is a rare congenital anomaly in which both testes migrate toward the same hemiscrotum. In most cases, the correct diagnosis is not made preoperatively, but it's made during an inguinal herniotomy or during surgical exploration for an undescended testis because TTE is clinically misdiagnosed as an symptomatic inguinal hernia or as a tumor of the testis on the side to which the ectopic testis has migrated or as an undescended testis on the contralateral side. US and MR imaging can detect the transverse testicular ectopia by its characteristic appearance and so provide useful information about any associated anomalies. We report here on a case of transverse testicular ectopia that was diagnosed by US and MR imaging in a 10-month-old boy, and we review the relevant literature.