Methods and compositions are provided concerning a bispecific chimeric antigen receptor (CAR) targeting BCMA and CS1, particularly in multiple myeloma patients. The bispecific CAR has advantages over dual or separate BCMA and CS1 CAR molecules. In some embodiments, there is a bispecific chimeric antigen receptor comprising a) a bispecific extracellular binding domain comprising both i) a BCMA-binding region and ii) a CSI-binding region; b) a single transmembrane domain; and, c) a single cytoplasmic region comprising a primary intracellular signaling domain.