The prognosis of patients with advanced hepatocellular carcinoma (HCC) with tumor thrombus extending to the inferior vena cava (IVC) is extremely poor. Herein, we present a rare case of advanced HCC that was treated with sorafenib and radiotherapy, leading to complete remission. This patient had a 9 cm infiltrative HCC occupying almost the entire left lobe with a tumor thrombus extending through the hepatic vein, IVC, and left portal vein. The patient received 400 mg sorafenib twice daily. One year after the start of sorafenib, intensity-modulated radiation therapy for viable HCC and tumor thrombus was performed with a dose of 5,500 cGy. Twenty-seven months after the starting date of sorafenib, there was no intratumoral arterial enhancement, which suggested a complete response according to the modified RECIST criteria. This case suggests that the combination of sorafenib and radiotherapy might provide clinical benefits in patients with advanced HCC with IVC tumor thrombus.