Mixed embryonal carcinoma-teratoma is defined a rare kind of germ cell tumor, especially in children. Objective: a rare case report with early puberty due to mixed embryonal carcinoma - teratoma. Subjective: a 3 year 7 month old boy presented with early puberty and adrenal tumor in National Hospital of Pediatrics. Method: a case report. Results: a 3 year 7 month old boy presented with enlargement of penis, acnes, pubic hair, deep voice. Abdoment ultrasound and CT scan showed adrenal tumor, serum laboratory showed: 17 OHP 3.8 ng/ml, testosteron 32.3 nmol/l, cortisol 8h 433.9 nmol/l, cortisol 22h 39.2 nmol/l, glucose 3.7 mmol/l, aFP 3945.9 u/l, electrolyte normal
urine VMA 15.5 umoI/24h
bone age 5 years. Surgical showed the tumor did not originate from the adrenal. Histologica showed mixed embryonal carcinoma - teratoma. After surgeon, the signs of virilization reduce, serum testosteron become normal. Conclusion: mixed embryonal carcinoma - teratoma can be caused testosterone excretion and early puberty.