Introduction: Gastric cancer is the fourth prevalent cancer and the second reason for cancer-associated mortalities worldwide. Caffeic acid phenethyl ester (CAPE) is one of the main medicinal components of propolis. The aim of this study was to investigate the morphological apoptotic changes and cytotoxic effects of CAPE in human gastric adenocarcinoma cell line (AGS cell). Methods: AGS human gastric cancer cell line was cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) medium in vitro. Cytotoxic effects and morphological changes induced by 72 h treatment with CAPE at different concentrations on AGS cells were investigated by MTT assay test and inverted microscope, respectively. Results: CAPE in a concentration dependent fashion reduced viability of AGS cells. IC50 was obtained approximately 10 μM at 72 h treatment. Also, CAPE induced concentration-dependent morphological apoptotic changes and promoted complete apoptosis program in AGS human gastric cancer cell line. Conclusion: Our results strongly suggest that CAPE stimulates apoptotic process and leads to cell death. Therefore, CAPE could be useful in developing chemotherapeutic agents for treating human gastric cancer.