A 2-year-old boy presented with pneumonia and an abdominal mass was noted incidentally. A right lobe hepatic mass classified as PRETEXT III and congenital absence of the portal vein with drainage of the superior mesenteric vein to the inferior vena cava (Abernethy malformation type I) were confirmed by computed tomography and angiography. After a clinical diagnosis of hepatoblastoma had been made, he was treated with 4 cycles of doxorubicin and cisplatin and hepatic arterial chemoembolization with doxorubicin, after which the tumor was classified as POSTEXT III. He underwent a right extended hepatic lobectomy with resection of the caudate lobe but died on postoperative day 4 due to hepatic failure. The Abernethy malformation type I is associated with the development of hepatic tumors, and the abnormal blood flow might predispose to hepatic failure after liver resection. Extensive study of the hepatic vasculature is warranted in patients with suspected malformations. Liver transplant could be considered in patients with congenital portosystemic shunt and malignant liver tumors.