The present invention is directed to a chimeric antigen receptor (CAR) fusion protein comprising from N-terminus to C-terminus: (i) a single-chain variable fragment (scFv) comprising VH and VL, wherein scFv binds to a tumor antigen, (ii) a transmembrane domain, (iii) a co-stimulatory domain of GITR intracellular domain, and (iv) an activating domain. In one embodiment, the tumor antigen is human epidermal growth factor receptor (EGFR), human mesothelin, or human CD19. CARs having GITR intracellular domain as a co-stimulatory domain have certain advantages over other traditional CAR co-stimulatory domains.