Background: Undifferentiated embryonal sarcoma of the liver (UESL) is a rare and highly aggressive primary hepatic mesenchymal malignancy that predominantly affects children and adolescents. It accounts for approximately 6–13% of pediatric liver tumors and is often associated with diagnostic challenges due to nonspecific clinical presentation, normal serum tumor markers, and complex radiologic features. Early recognition and multimodal management are essential to improve outcomes. Case Presentation: We report two adolescent patients, aged 9 and 16 years, who presented with progressive right upper quadrant abdominal pain and hepatomegaly. Laboratory investigations, including alpha-fetoprotein (AFP), were within normal limits in both cases. Imaging studies revealed large, well-defined hepatic masses with heterogeneous cystic-solid characteristics. In one case, radiologic finding initially suggested a giant hemangioma. Both patients underwent major hepatic resection. Gross examination demonstrated large, well-circumscribed tumors with solid, cystic, hemorrhagic, and necrotic components. Histopathology revealed highly cellular neoplasms composed of anaplastic spindle and stellate cells within a myxoid stroma, with prominent eosinophilic hyaline globules and brisk atypical mitoses. Immunohistochemistry showed positivity for vimentin and alpha-1 antitrypsin, confirming the diagnosis of UESL. Postoperative follow-up revealed early peritoneal metastasis in one patient, while the other developed multiple recurrences and died six months after surgery. Conclusion: UESL should be strongly considered in adolescents presenting with large hepatic masses and normal AFP levels, particularly when imaging demonstrates discordant cystic-solid characteristics. Accurate diagnosis relies on careful radiologic–pathologic correlation and immunohistochemical confirmation. Complete surgical resection combined with adjuvant chemotherapy remains the cornerstone of treatment; however, recurrence and metastatic spread remain significant challenges. Early multidisciplinary management and close postoperative surveillance are critical to improving survival outcomes.