The transforming growth factor-β (TGF-β) signaling pathway exhibits an important role in cancer invasion and metastasis. Excessive expression of TGF-β activates Smad4, leading to the upregulation of downstream metastasis-associated genes. Thus, the inhibition of the TGF-β/Smad4 signaling pathway may be a novel strategy for treatment of cancer metastasis. Baicalein, a flavonoid derived from the root of Scutellaria baicalensis, has been reported to exert strong anti-tumor activity towards various types of cancer. In the present study the effect of baicalein on migration and invasion of cancer cells was evaluated using wound-healing and Transwell assays. In order to investigate the possible molecular mechanisms of the anti-metastatic effects of baicalein, quantitative polymerase chain reaction (qPCR) and western blot analyses were performed to examine the effect on the expression of TGF‑β, Smad4, N-cadherin, vimentin, ZEB1 and ZEB2. It was determined that baicalein inhibited the migration and invasion of AGS cells by suppressing the TGF-β/Smad4 signaling pathway. In addition, baicalein treatment reduced the expression of the metastasis-associated N-cadherin, vimentin, ZEB1 and ZEB2, downstream target genes of the TGF‑β/Smad4 signaling pathway. Collectively, these results suggest that inhibition of the metastasis of cancer cells via inactivation of TGF-β/Smad4 signaling is one of the mechanisms by which baicalein may treat cancer.