Curcumol, a polyphenol compound derived from the rhizome of Curcuma, has been established as an antitumor compound against multiple types of cancer, including gastric (GC), lung, liver and breast cancer. However, the molecular mechanisms undelying its anticancer activity in GC are still unclear. In this study, the antitumor efficacy of curcumol was ascertained in human gastric adenocarcinoma MGC-803 cells. An MTT assay was used to assess the viability of the MGC-803 cells treated by curcumol. The results of the Annexin V/propidium iodide (PI) staining followed by fluorescence activated cell sorting (FACS) analysis demonstrated that the cell cycle was arrested in the G2/M phase by curcumol. Annexin V-FITC/PI double staining followed by FACS analysis revealed that curcumol induced apoptosis of MGC-803 cells. FACS analysis after the cells were loaded with a DFCH-DA probe revealed that the level of reactive oxygen species (ROS) increased after the cells were treated with curcumol. In adittion, FACS analysis after the cells were loaded with JC-1 revealed that the level of mitochondrial membrane potential (MMP) decreased after the cells were treated with curcumol. Furthermore, the downregulation of isocitrate dehydrogenase 1 (IDH1) was observed in the MGC-803 cells after being treated with curcumol as determined by western blotting and RT-qPCR. In conclusion, we elucidated the antitumor effect of curcumol on MGC-803 cells and the involved mechanisms related to the induction of apoptosis, the increase of ROS, the decrease of MMP and the downregulation of IDH1.