Mixed germ cell tumors are very rare in young females. Patient survival, preservation of ovarian function and fertility are becoming an important issue. A locally advanced (III), bulky malignant mixed germ cell tumour in a 12-year-old girl presented to the Department of Radiotherapy, Regional Institute of Medical Sciences, Imphal, Manipur, in January 2011 with abdominal distension for one month. On physical examination, there was a large lower abdominal mass approximately 16x14 cm(2). Abdominal and pelvic CTs showed a lobulated 19x15x10 cm soft tissue attenuation mass lesion in the pelvis extending superoanteriorly to supra-umbilical area. Laboratory investigations revealed increased serum LDH (4,245 IU/L) and serum beta-hCG (105.4 mIU/ml). Ultrasonography (USG)-guided fine needle aspiration cytology (FNAC) from left ovarian mass was suggestive of malignant germ cell tumour. In view of bulky and advanced stage, patient was administered four cycles of neoadjuvant chemotherapy (inj. ifosphamide 1,440 mg, inj. etoposide 90 mg, inj. cisplatin 24 mg for D15, four weekly) followed by left salpingo-oophorectomy with wedge biopsy of right ovary and partial omentectomy, and another two cycles of adjuvant chemotherapy with same regimen. Biopsy tissue histopathology report also confirmed mixed germ cell tumour. Patient was kept on regular follow-up and she has been disease-free for the last four years. The present authors' treatment policy in such bulky and advanced tumor in adolescents is effective.