Background: Malignant melanoma is a rare malignancy in the pediatric population. Etiology is usually unknown. Clinical symp toms are non-specifi c, clinical behavior and biology features may differ from those in an adult population. The most important prognostic factor is spread of dis ease. Surgical resection is treatment of choice for localized melanoma. Advanced and metastatic melanoma is still an incurable disease. Case: We are presenting an eight-year- old boy with metastatic malignant melanoma of unknown origin based on TP53 mutation (Li- Fraumeni syndrome). He underwent surgery and adjuvant chemotherapy (temozolomide as single agent). Complete remission was achieved at the end of treatment. Two years after the end of therapy (and 31 months from diagnosis) he developed metastatic progression to the lungs. He has received immunotherapy with ipilimumab, according to our knowledge as the first child under the age of 12 in Europe. He completed three courses of ipilimumab, with irAE (immune related adverse event) grade III during the first course of anti CTLA- 4. Therefore, further doses of ipilimumab were given with corticoids and antihistamines as premedication. Also, asymp tomatic thyreoiditis grade II has been confirmed. The best documented treatment response is stable disease. Performance status was excellent. Three years since the first progression, he developed further massive progression to the lungs. Second line immunotherapy with anti-PD- 1 monoclonal antibody (pembrolizumab) is currently going on. So far, the overall survival of the patient is 74 months. Conclusion: The presented case study supports the administration of immunotherapy in children younger than 12 years. Therapeutic effect has led to significant overall survival with tolerable toxicity. The problem remains significantly limited number of pediatric clinical trials using immunotherapy.