Three traditional Chinese medicines, Agrimonia pilosa Ledeb, Grifola umbellata (pers.) Pilat, and Gambogia, are combined to form a compound extract, AGC. In this study, the in vitro and in vivo inhibitory effects of AGC on human gastric carcinoma MGC-803 cells were demonstrated, and the molecular mechanisms underlying these effects are investigated. Our results indicate that AGC inhibited MGC-803 cell growth in a dose-dependent manner as measured by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, with an $IC_{50}$ of about $6.045{pm}0.69{mu}g/mL$. In vivo, AGC inhibited growth of human gastric carcinoma in xenograft tumors in nude mice, and the inhibitory rate reached 55.2% at 300 mg/kg. The pro-apoptotic activity of AGC was attributed to its ability to decrease the expression of Bcl-2 and Pro-caspase3 and increase the expression of Bax. These results demonstrate that AGC can effectively induce programmed cell death and may be a promising anti-tumor drug in human gastric carcinoma.