Accumulating evidence has indicated that garlic consumption may reduce the risk of developing several types of cancer, and extensive studies have revealed the effects of its bioactive component, diallyl trisulfide (DATS), on the proliferation and apoptosis of tumor cells. The present study was undertaken to examine whether DATS affects hematogenous metastasis. In view of the dynamic crosstalk interplayed by tumor cells and platelets in hematogenous metastasis, we attempted to demonstrate the role of DATS in the metastatic behavior of MDA-MB-231 human breast cancer cells, which were co-incubated with activated platelets. Indeed, our data indicated that DATS significantly blocked platelet activation and aggregation induced by platelet-activating factor (PAF), and decreased the production of thromboxane B2 (TXB2). It was also found that DATS suppressed the migration and invasion of MDA-MB-231 cells in the presence of platelets activated by PAF in vitro in a dose-dependent manner. Furthermore, our results revealed thaat the release of activated TGF-β1 in the platelet-tumor cell system was markedly attenuated by DATS. Therefore, our findings strongly suggest that the diverse pharmacological activities of DATS are at least partially reflected by the interruption of the activated platelets-mediated metastasis of breast cancer cells.