Abstract : Teratoma is the second most common germ cell tumor type in the pediatric and adolescent age group and is found as a component in 50% of mixed germ cell tumors. Very rarely during or following chemotherapy for mixed germ cell tumors, enlarging residual masses appear consisting of only mature teratoma components which is called growing teratoma syndrome. A 16-year adolescent male presented with painless left testicular swelling. Radiological and biochemical investigations including serum tumor markers were performed. Left high inguinal orchidectomy was done which on histopathological examination revealed mixed germ cell tumor comprising of seminoma and embryonal cell carcinoma. Chemotherapy was started to which patient responded. After 3 months follow up PET scan revealed faint to low grade FDG avid multiple lumps or lymph nodal masses in the lung and abdomen, which were removed surgically. The serum tumor markers were within normal limits. Histopathological examination from all the masses showed mature teratoma component only while lung showed necrosis only. Hence the diagnosis of growing teratoma syndrome was considered. One should be aware of this rare entity and it is necessary to diagnose it in order to prevent unnecessary chemotherapy and allow optimal management. Prognosis is excellent after the complete excision of this tumour. It is usually found in non seminomatous GCTs but very rare to be found in mixed GCTs. The present case was a diagnostic challenge as it was spread throughout the body and mimicked metastasis.