We report a 46-year-old male patient with functional liver damage due to hepatitis B virus infection. A 12 cm hepatocellular carcinoma (HCC) in the left lobe and portal venous tumor thrombosis (PVTT) with vp4 (portal vein tumor thrombosis in the main trunk) were detected by computed tomography (CT). He underwent hepatic arterial infusion chemotherapy (HAIC) with cisplatin 100 mg for HCC and received radiation therapy (39 Gy/13 Fr) for PVTT with vp4. Follow-up CT showed reduction of HCC and reduced PVTT volume after 1 month of treatment. He then initiated lenvatinib therapy at 12 mg/day. One month later, follow-up CT showed no change in HCC size and a reduction in PVTT volume. Two months after initiating lenvatinib, follow-up CT showed no change in HCC, but further reduction in contrast effect and volume of PVTT. Three months after HAIC, he underwent drug-eluting-bead transcatheter arterial chemoembolization (DEB-TACE) with 100 mg of cisplatin (CDDP) for the HCC. After DEB-TACE, he received 12 mg/day with 5-days-on/2-days-off due to vomiting. One month after DEB-TACE, blood evaluation showed decreased tumor markers, and CT revealed that the HCC had grown slightly with no change in PVTT. Five months after HAIC, he underwent DEB-TACE with 100 mg of cisplatin for the HCC. A total of 150 days have passed since the start of lenvatinib treatment, and his Child-Pugh A status has been maintained.