We herein describe a 9-month-old boy who presented with bilateral scrotal hydroceles shortly after birth. The right hydrocele spontaneously resolved during this period, and a nonpalpable testis of the right side was noted. In contrast, the left hydrocele gradually increased in size. Ultrasound and magnetic resonance investigations performed at the age of 7 months could not detect the right testis either in the inguinoscrotal region or the abdominal cavity. These examinations also pointed out a huge hydrocele that extended from the left scrotum to the abdominal cavity. At the age of 9 months, a laparoscopic-assisted operation for both the right undescended testis and the left abdominoscrotal hydrocele (ASH) was performed. During the operation, an atrophic testis secondary to in utero intravaginal torsion was shown on the right inguinal region, and a huge ASH was revealed in the left inguinoscrotal region. The finding of the left ASH was confirmed by a laparoscope inserted through the processus vaginalis of the right side. At first, the processus vaginalis of the left side was highly ligated by the inguinal approach, and then the ASH was opened and its wall was resected. Our findings suggest that both an understanding of the pathogenesis and a corrective operation of ASH can be made via the inguinal approach. In cases associated with cryptochidism owing to an intraabdominal testis or an in utero extravaginal torsion, a laparoscopic-assisted operation may therefore be useful both for making a precise diagnosis and for surgically removing an ASH.