Background: Postoperative adjuvant transcatheter arterial chemoembolization (PA-TACE) can achieve longer overall survival (OS) and disease-free survival (DFS) in hepatocellular carcinoma (HCC) patients with microvascular invasion (MVI). We investigated whether this treatment strategy could benefit these patients by mediating the dysfunctional immunological status. Therefore, a retrospective cohort study was conducted to investigate the effect of early PA-TACE in HCC patients with MVI by measuring the levels of T helper cell 17 (Th17) and regulatory T cell (Treg)., Methods: This study retrospectively included 472 patients with HCC undergoing hepatectomy between December 2015 and December 2018, and 115 patients with MVI confirmed by postoperative pathology were enrolled and divided into two groups of TACE group and non-TACE group according to whether TACE was performed. HCC patients with MVI. The proportion of Treg and Th17 cells in peripheral blood was measured one day before and four weeks after TACE. All patients in the two groups were followed up until death or until the study ended in December 2023. The rates of OS and progression-free survival (PFS) in patients with MVI were compared between those who received hepatectomy alone and those who underwent early PA-TACE., Results: Among 115 HCC patients with MVI from 472 patients, the study enrolled 51 patients with PA-TACE into the TACE group and 42 patients without TACE into the non-TACE group. There were no statistical differences in baseline data between the two groups (all P>0.05). The frequency of Treg among CD4+ T cells in HCC patients with PA-TACE was significantly lower than baseline (7.34%±3.61% vs . 5.82%±2.76%, P<0.001), and the frequency of Th17 among CD4 + T cells in these patients was significantly higher than baseline (0.49%±0.28% vs . 0.50%±0.25%, P<0.001). Among all the patients, the median OS was 61.8 months. The OS rate and PFS rate at 12, 36, and 60 months in the TACE group were significantly higher than those in the non-TACE group (all P<0.05)., Conclusions: PA-TACE may have roles in improving survival outcomes, and restoring immune homeostasis in HCC patients with MVI after hepatectomy., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jgo.amegroups.com/article/view/10.21037/jgo-24-282/coif). All authors report that this study was supported by the Chinese Foundation for Hepatitis Prevention and Control-Tian Qing Liver Disease Research Fund Subject 20200098 (TQGB20200098); and Beijing iGandan Foundation (iGandanF-1082022-RGG044). The authors have no other conflicts of interest to declare., (2024 Journal of Gastrointestinal Oncology. All rights reserved.)