Therefore, we described a case of a 2-year-old pediatric patient with a giant testicular yolk sac tumor that was misdiagnosed by ultrasonography as orchitis, in order to evaluate the role of measuring AFP levels in the initial diagnosis to aid in the accuracy of the definitive diagnosis of testicular yolk sac tumor.<h4>Case presentation</h4>A 2-year-old boy received outpatient visits for unintentional swelling of the right scrotum for 7 days. Here, AFP is linked to yolk sac tumor.