Mucin 1 (MUC1) is large glycoprotein, expressed in most of the adenocarcinomas and involved in tumor progression, metastasis and transformation. MUC1 has large, glycosylated, extracellular domain with different number of tandem repeates (20 amino acid), transmembrane region and a cytoplasmic tail. Over expression of MUC1 gene products are reported in different carcinoma condition includes breast cancer, gastrointestinal cancer, overian cancer, pancriatic cancer, lung cancer and Lymphomas. In this study we have highlighted the involvement of MUC1 gene at different level, mechanism of action and therapeutic approach in breast cancer.