Introduction: Oxidative stress plays a key role in ischemic-reperfusion (IR) injury. Recent studies have shown that endoplasmic reticulum (ER) stress in the tubular cells of kidneys is associated with IR injury. However, there is little information about the anti-apoptotic cytokines that help overcome ER stress in HK-2 cells. In this study, we investigated the effect of interleukin-22 on H2O2-induced apoptosis and ER stress in HK-2 cells. Methods: For this study, we used the HK-2 cell line to examine interleukin-22 toxicity and its therapeutic concentrations using XTT test. H2O2-induced injury is well known as an oxidative stress model for acute kidney injury. We stimulated HK-2 cells with H2O2, which induced apoptosis. The expression of ER stress marker proteins, such as glucose-regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), phosphorylated eukaryotic translation initiation factor 2 alpha (p-eIF2α), and C/EBP homologous protein (CHOP), were evaluated by western blot analysis. Results: In HK-2 cells, H2O2 increased the levels of apoptotic proteins that cleaved PARP in a dose-dependent manner at 4 h. ATF4, p-eIF2α, and C/EBP homologous protein (CHOP) were also increased by H2O2 stimulation. Interleukin-22 pre-treatment prevented H2O2-induced apoptosis and decreased expression of these ER stress proteins in HK-2 cells as observed through western blot analysis. Interleukin-22 blocking antibody abolished interleukin-22 induced protective effects on HK-2 cells. Conclusions: Our results suggest that interleukin-22 prevents H2O2-induced apoptosis in HK-2 cells through suppression of ER stress. Therefore, interleukin-22 can potentially be an anti-apoptotic cytokine for IR injury.