Background: In the present study, the cytotoxic effects of the combination of metformin with docetaxel and 5-fluorouracil were studied on AGS gastric cancer cell line. Methods: In this experimental study, the cells were exposed to different concentrations of metformin (1-80 mM), docetaxel (0. 6-22. 5 ng/ml), 5-fluorouracil (0. 045-12 μ g/ml), and combination of them. The cell proliferation was evaluated using MTT assay, and the cell apoptosis was evaluated by acridine orange/ethidium bromide assay. Findings: Metformin, docetaxel, and 5-fluorouracil inhibited cell viability of AGS gastric cancer cells in a concentration-and time-dependent manner. The half-maximal inhibitory concentration (IC50) values were decreased after treatment with metformin/docetaxel and metformin/5-fluorouracil (P < 0. 050). Moreover, the combination treatments significantly increased apoptosis of gastric cancer cells (P < 0. 050). Conclusion: Our results showed that the combination of metformin with docetaxel and 5-fluorouracil could be effective in the treatment of patients with gastric cancer.