The inhibitory effect of resveratrol on the growth of gastric cancer cells through downregulation of the Wnt/β-catenin signaling pathway were studied. First we determined the effective concentration of resveratrol on the growth and proliferation of MGC-803 gastric cancer cells. Methylthiazolyl tetrazolium assay showed that resveratrol significantly inhibited the proliferation of MGC-803 cells in a dose-dependent manner. Resveratrol induced apoptotic morphological changes in MGC-803 cells. Reverse transcription-polymerase chain reaction and western blot analysis showed that resveratrol downregulated the expression of three important components of the Wnt signaling pathway, β-catenin, c-myc, and cyclin D1, at the mRNA and protein levels. Overall, resveratrol inhibits the growth of MGC-803 cells by inhibiting the Wnt signaling pathway. This study provides a new idea and direction for the antitumor mechanism of resveratrol.