Background: To compare the efficacy and safety of sorafenib plus transarterial chemoembolization (SOR-TACE) versus sorafenib alone as postoperative adjuvant therapy for hepatocellular carcinoma (HCC) patients with portal vein thrombus (PVTT). Methods: This was a phase III, multicenter, randomized, control clinical trial. Eligible HCC patients with PVTT were included and randomly assigned (1:1) to receive SOR-TACE or sorafenib alone as postoperative adjuvant therapy. Sorafenib treatment was started within 3 days after randomization, with an initial dose of 400mg twice a day. In the SOR-TACE group, TACE was performed one day after the administration of sorafenib. The primary endpoint was recurrence-free survival (RFS). Results: From October 2019 to March 2022, a total of 158 HCC patients with PVTT from China were enrolled and randomized. After a median follow-up duration of 28.4 months, the median RFS was significantly longer in the SOR-TACE group (16.8 vs. 12.6 months; hazard ratio, 0.57; P = 0.002). The median overall survival (OS) was also significantly longer with SOR-TACE than with sorafenib (30.4 vs. 22.5 months; hazard ratio, 0.57; P = 0.017). Multivariable analysis indicated SOR-TACE treatment was an independent risk factor for both RFS and OS. The SOR-TACE group did not show additional toxicity compared with the sorafenib alone group. Conclusions: The combination of sorafenib and TACE as postoperative adjuvant therapy in HCC patients with PVTT resulted in longer RFS and OS compared to sorafenib alone and was well tolerated. Clinical trial information: NCT04143191.