Abstract: Objective To investigate the effect of diallyl disulfide (DADS) on invasion and metastasis of human breast cancer MCF-7 cells and explore the possible mechanism. Methods MCF-7 cells treated with 100, 200, and 400 μmol/L of DADS for 24 h were examined for cell invasion and migration capacities using Transwell assay and wound healing assay, respectively. The protein expression of E-cadherin, vimentin, MMP-9 and p-p38 in the cells were detected with Western blotting. The effect of transforming growth factor-β1 (TGF-β1) as the agonist of p38 activity was tested in antagonizing the effects of DADS. Results DADS inhibited the invasion and migration of MCF-7 cells in a dose-dependent manner, down-regulated the protein expression of Vimentin and MMP-9 and up-regulated E-cadherin expression in the cells. Treatment with TGF-β1 to up-regulate p38 activity obviously antagonized the inhibitory effect of DADS on the invasion and metastasis of MCF-7 cells. Conclusion DADS can inhibit the invasion and metastasis of MCF-7 cells in vitro by down-regulating p38 activity.