Tumor relapse is the main cause of breast cancer related deaths and metastasis due to epithelial -mesenchymal transition (EMT) having a critical role in this process. MAML1 is the main co activator of NOTCH signaling pathway and its role in EMT remains unknown. In this study, this role was evaluated through overexpression and knockdown study of MAML1 in MCF7 and MDA-MB-231 cells. MAML1 overexpression up regulated the epithelial and down regulated the mesenchymal markers. In addition, MAML1 silencing decreased epithelial and increased mesenchymal markers. Notch inhibition using gamma-secretase inhibitor resulted in increased E-cadherin expression. MAML1 ectopic expression, further increased E-cadherin expression with inhibition of NOTCH signaling. Wound healing assay showed that MAML1 overexpression decreases the rate of migration, while MAML1 silencing increases this rate significantly. In conclusion, our data indicated that MAML1 negatively regulates EMT markers expression in breast cancer cells. (C) 2019 Published by Elsevier Inc.