Breast cancer (BC) is a commonly diagnosed cancer amongst women and the second leading cause of cancer deaths in the world. BC has created huge challenges to healthcare providers regarding the identification of main risk factors and how they contribute to the development of the disease. Several studies suggest that biological risk factors such as duration of breast feeding, age at menarche, menopausal status and the use of contraceptive pills have contributed to the increase of BC diagnoses. Moreover, psychological factors such as depression, stress and negative lifestyles are gaining more attention as a major contributor to this type of cancer. The role of psychological stress regarding BC has been widely demonstrated in the literature across several fields including but not exclusive to epidemiology, physiology, and molecular biology which all show a clear relationship between intracellular stress signaling and protumorigenic pathways within breast cells. Cortisol is primary stress hormone of the human body and a growing body of research both clinically and molecularly are revealing a positive correlation of high cortisol levels and the progression of BC. This review attempts to establish and highlight how cortisol levels impact breast cancer development and progression.