Of all primary retroperitoneal teratomas, less than four percent occur in children and 90% are benign. we report a case of mature retroperitoneal teratoma in a 4 months year old girl. She presented with right side, slow growing, abdominal mass since 1 month; Ultrasound of abdomen found Large right suprarenal mass, of multiloculated cysts, containing stalls of variable size and thick septa. Computed tomography (CT) assessed the vascular and visceral anatomical relationships. Patient underwent surgery, the tumor was separeted from all adherent tissus with complete resection. Without vascular and organs injuries. Histopathological examination of tumor was suggestive of mature teratoma. Post operative recovery was favorable and patient was discharged from the departement. The oncologic outcome of retroperitoneal teratoma is positive especially with complet resection.