Pure yolk sac tumor is the most common malignant testicular germ cell neoplasm in pediatric age. A case of a pure yolk sac tumor of testicle in a pediatric patient is presented. A 3-year-old male patient who presented painless scrotal volume increase, hard consistency and insidious onset. Increased scrotal volume with a single, hard, ovoid, painless tumor of firm consistency and little mobile was observed. Serum alpha-fetoprotein values were elevated. Ultrasound evaluation showed an increase in volume of right testicle with a homogeneous tumor. Magnetic resonance imaging showed a large, vascularized, well-defined and heterogeneous tumor in right testicle. During surgery, it was observed that the right testicle was occupied by a well-delineated tumor of hard consistency and some cystic elements that closely adhered to neighboring structures. Findings led to diagnosis of a pure yolk sac tumor of right testicle. In general, the pure yolk sac tumor appears as an asymptomatic testicular lesion in pediatric patients. Most pediatric cases are diagnosed in stage I, so radical orchiectomy is therapeutic. Chemotherapy is only indicated in cases with metastases or recurrences.