An undifferentiated embryonal sarcoma of the liver (UESL) is a rare and highly malignant mesenchymal neoplasm that is uncommonly observed in adults. We report a case of UESL found in a 26-year-old female. Our case was initially regarded as a type II hydatid cyst and then a malignant mass in radiological studies. The patient underwent nonanatomic liver resection. There were postoperative complications, but they were handled successfully. The patient received taxol-cisplatin-ifosfamide chemotherapy protocol and is disease-free after six years. Although UESL is exceedingly rare in adults, it must be considered while evaluating large hepatic masses since curative resection has an excellent prognosis.