Sarcomas represent less than 1% of all malignant tumors. Undifferentiated Embryonal Sarcoma (UES) of the liver is the third most common pediatric liver cancer. The main differential diagnoses are mesenchymal hamartoma, hepatoblastoma, and biliary embryonal rhabdomyosarcoma. Definitive diagnosis is confirmed by histopathology and immunohistochemical. 4-year-old male patient with fever, abdominal pain and palpable hepatomegaly was found. Magnetic Resonance Imaging (MRI) with an unifocal cystic hepatic mass, with compression and displacement of vascular structures, but without invasion; hamartoma was suspected. The management was a right hepatectomy. Immunohistochemistry studies were positive for UES. Adjuvant chemotherapy was started with a good response.