BACKGROUND: Immunogenic cell death (ICD) is a distinct subtype of regulatory cell death, and represents a potential mechanism to remodel the tumor microenvironment. Lenvatinib is established as the first-line therapy for advanced hepatocellular carcinoma (HCC), but drug resistance limits its efficiency. Our previous research showed that lenvatinib can inhibit GPX2 expression and induce reactive oxygen species (ROS)-related cell apoptosis in HCC. The present study intends to explore whether lenvatinib can induce ICD and clarify its underlying mechanisms in HCC. METHODS: Flow cytometry was utilized to detect the expression levels of CRT and CD markers, measure intracellular ROS levels, and assess cell apoptosis. Western blot analysis was employed to determine changes in protein levels, while qRT-PCR analysis was used to quantify alterations in mRNA levels. Subcutaneous allograft tumor models were established to investigate the mechanism of lenvatinib against HCC. Immunohistochemical (IF) staining were used to detect the ratio of CD8GZMB cells. RESULTS: Herein, we found that HCC cells treated with lenvatinib or si-GPX2 showed increased ICD markers, such as CRT exposure, ATP secretion, and HMGB1 release. Notably, we demonstrated that lenvatinib promoted dendritic cells (DCs) maturation and CD8+ T cells activation, thus inducing HCC cell apoptosis when co-cultured with peripheral blood mononuclear cells. Additionally, we further demonstrated that lenvatinib or GPX2 inhibition triggers endoplasmic reticulum stress (ERS) in HCC cells, which is mediated by the accumulation of ROS. Our findings indicate that pre-treatment with the antioxidant N-acetylcysteine suppressed lenvatinib-induced expression of CRT on the cell membrane, ATP secretion and HMGB1 release, and inhibited lenvatinib-induced cell apoptosis. Furthermore, we also found that ERS inhibitor ISRIB could reverse lenvatinib-induced upregulation of ICD biomarkers. Moreover, we further identified that downregulation of GPX2 enhanced the efficacy of lenvatinib via triggering ERS-mediated ICD in HCC. CONCLUSIONS: This study uncovered that lenvatinib could be a potent ICD inducer, which could trigger ERS via increasing ROS levels in HCC cells, which present valuable insights into the mechanism of lenvatinib-induced ICD in HCC cells. Collectively, our findings highlight the significant therapeutic potential of the combination of targeting GPX2 and treatment with lenvatinib for HCC.