Juvenile granulosa cell tumors (JGCT) of the ovary are rare in children and adolescents. About 90% are diagnosed in early-stage FIGO I with favorable prognosis. More advanced stages (FIGO II-IV) have a poor clinical outcome and chemotherapy alone cannot avoid tumor progression. Regional deep hyperthermia (RHT) induced by microwave technique has been established as an additional modality for treatment of different tumors. However, in cases with liver involvement there are technical problems which have not yet been solved. We report on a 4-year-old child who suffered from diffuse liver metastases 10 months after JGCT of the left ovary. After chemotherapy including ifosfamide, etoposide, and carboplatin in combination with RHT and consolidation radiotherapy, the patient has been in complete remission for 1 year of follow-up. This Case Report indicates the feasibility of combining surgery, chemotherapy, hyperthermia, and radiation therapy (which can also be an effective treatment modality for advanced granulosa cell tumor) for the treatment of liver metastases of JGCT, but does not allow comparisons of these treatments.