Purpose: The epithelial-to-mesenchymal transition (EMT) is the main event that favors cell migration and metastasis in breast cancer. Previously, we demonstrated that 1 nM estradiol (E2 ) promotes EMT, induced by c-Src kinase, causing changes in the localization of proteins that compose the tight junction (TJ) and adherens junction (AJ). Methods: The present work highlights the central role of c-Src in the initiation of metastasis, induced by E2 , through increasing the ability of MCF-7 and T47-D cells, which express estrogen receptor alpha (ERα), to migrate and invade before they become metastatic. Results: Treatment with E2 can activate two signaling pathways, the first one by the phosphorylated c-Src (p-Src) which forms the p-Src/E-cadherin complex. This phenomenon was completely prevented by incubation with a selective inhibitor of c-Src (5 µM PP2).p-Src then promotes the downregulation of E-cadherin and occludin, which are epithelial phenotype marker proteins of the AJ and TJ, respectively. In the second pathway, E2 binds to ERα, creating a complex that translocates to the nucleus, inducing the synthesis of SNAIL1 and N-cadherin proteins, markers of the mesenchymal phenotype. Both processes increased the migratory and invasive capacities of both cell lines. Conclusion The present study demonstrate that E2 enhance EMT and migration, through c-Src activation, in human breast cancer cells that express ERα and become potential therapeutic targets.