Background: An abdominoscrotal hydrocele (ASH) is a rare lesion and should be considered in the differential diagnosis of abdominal cystic lesions in boys. Case Report: We report a case of a 4-month-old boy with a thin-walled, anechoic cystic abdominal mass in ultrasound (US) examination. As the size of the lesion increased in follow-up US after one month, computed tomography (CT) was performed. CT demonstrated a communication between a cystic mass in the abdomen and a right scrotal hydrocele - an abdominoscrotal hydrocele (ASH). The patient had no symptoms and was observed by means of US examination. After the next 4 months, the size of the ASH decreased remarkably. Conclusions: This rare entity should be considered in differential diagnosis of cystic abdominal masses in boys. Spontaneous resolution of ASH is rare, but asymptomatic patients can be followed up before surgery.