Immunotherapeutic treatment strategies for metastatic breast cancer have thus far focused largely on checkpoint inhibition, with atezolizumab and pembrolizumab comprising currently approved options in combination with chemotherapy in eligible patients. Chimeric antigen receptor (CAR) T cell therapy has demonstrated effective and durable disease control for patients with B cell hematological malignancies, leading to approvals for hematological indications by the U.S. Food and Drug Administration; however, to date, CAR T efforts have been less successful in solid tumors likely due to restricted trafficking into, infiltration of, and activation within tumors, in the context of potentially immunosuppressive tumor microenvironments. Additional challenges include on-target, off-tumor effects due to the presence of tumor-associated antigens in physiological tissues. Emerging strategies evaluating adoptive transfer of CAR T cells are focusing on improved design and manufacturing to circumvent these obstacles. This review summarizes the rationale, historic development of, and emerging strategies for CAR T therapy in breast cancer.