Back ground: Growing teratoma syndrome is a rare entity characterized by growing tumor mass in different locations (like retroperitoneum, abdomen, pelvis, liver, chest, bone, or lymph nodes) in patients with non-seminomatous germ cell tumors of ovary or testis, during or after chemotherapy. Tumor markers will be normal. Histopathological examination confirms the diagnosis. Case report: We report a case of 29 years old male presenting with slow growing retroperitoneal mass after complete treatment for non-seminomatous germ cell tumor of testis. Conclusion: Growing teratoma syndrome occurs in patients with non-seminomatous germ cell tumors and have serum tumor markers with in normal limits. Early diagnosis of this condition helps for complete curative resection of the tumor for better prognosis.