Cancer immunotherapy has witnessed a new renaissance with the advent of immune checkpoint inhibitors, which reactivate T cells and foster endogenous anti-tumor responses. The excellent results of immunotherapy in the field of melanoma, renal cancer, lung cancer, and other cancer types that have traditionally been known to be immunogenic, rekindled the interest of the oncology community in extending the benefits to all cancers including breast cancer (BC). In this review, we highlight the current state of using T cells as both markers for clinical practice and therapeutic options for BC.