Exosomes are released by normal and tumour cells, including those involved in breast cancer, and provide a means of intercellular communications. Exosomes with diameters ranging between 30-150 nm are involved in transferring biological information, via various lipids, proteins, different forms of RNAs, and DNA from one cell to another, and this can result in reprogramming of recipient cell functions. These vesicles are present in all body fluids, for example, blood plasma/serum, semen, saliva, cerebrospinal fluid, breast milk, and urine. It has been recently reported that these particles are involved in the development and progression of different tumor types, including breast cancer. Furthermore, it has been suggested that exosomes have the potential to be used as drug transporters, or as biomarkers. This review highlights the potential roles of exosomes in normal and breast cancer cells and their potential applications as biomarkers with special focus on their potential applications in treatment of breast cancer.