Gallic acid (GA), a polyhydroxylphenolic compound abundantly distributed in plants, fruits, and foods, has been reported to have various biological activities including an anticancer effect. In this study, we extensively investigated the anticancer effect of GA in human breast carcinoma MCF-7 cells. Our study indicated that treatment with GA resulted in inhibition of proliferation and induction of apoptosis in MCF-7 cells. Then, the molecular mechanism of GA's apoptotic action in MCF-7 cells was further investigated. The results revealed that GA induced apoptosis by triggering the extrinsic or Fas/FasL pathway as well as the intrinsic or mitochondrial pathway. Furthermore, the apoptotic signaling induced by GA was amplified by cross-link between the two pathways. Taken together, our findings may be useful for understanding the mechanism of action of GA on breast cancer cells and provide new insights into the possible application of such compound and its derivatives in breast cancer therapy.