Glutathione peroxidase 8 (GPx8) belongs to a family of enzymes that have a critical role in controlling levels of reactive oxygen species (ROS). GPX family members have been associated with several cancers. Here, we examined the role of GPx8 in esophageal squamous cell carcinoma (ESCC). Immunohistochemical staining and western blot analysis were used to study the clinical significance of GPx8 in ESCC tissue. GPx8 was further evaluated in cells by MTT assay and colony formation. RT-PCR, western blot, immunofluorescence staining, TUNEL assay, TEM, and flow cytometry were used to assess the molecular mechanism underlying endoplasmic reticulum (ER) stress associated with GPx8 in ESCC cells. Xenografted tumor growth was used to assess the in vivo role of GPx8. We found that GPx8 was overexpressed in both ESCC cell lines and tumor tissue. GPx8 knockdown significantly suppressed ESCC proliferation and induced autophagy and apoptosis in ESCC cell lines, whereas GPx8 overexpression led to increased proliferation and inhibition of apoptosis. GPx8-mediated inhibi-tion of apoptosis was associated with the ER stress pathway through inositol-requiring enzyme 1 (IRE1) and Jun N-terminal kinase (JNK). Knockdown of GPx8 in xenograft models of ESCC resulted in a significant reduction in tumor weight and volume, which was further reduced with IRE1 or JNK inhibitors. Our study suggests that GPx8 regulates apoptosis and autophagy in ESCC through the IRE1/JNK pathway in response to ER stress. Targeting this pathway might be a potential therapeutic strategy for ESCC.