Polycaprolactone (PCL) has been widely,adopted as scaffold biomaterial, but further: improvement of the hemocompatibility of a PCL film surface is still needed for wide biomedical applications In this work, the PCL film surface Was functionalized (3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (P(DMA PS)) brushes via; surface-initiated atom transfer radical polymerization (ATRP) for enhancing hemocompatibility. Kinetics study revealed an approximately linear increase in yield of the functional P(DMAPS) brushes with polymerization time: The blood compatibilities of the modified PCL film surfaces were studied by platelet adhesion tests of: platelet-rich plasma and human whole blood, hemolysis assay, and plasma; recalcification time (PRT) assay. The improvement of hemocompatibility is dependent on the coverage of the grafted P(DMAPS) brushes on the PCL film. Lower or no platelet and blood cell adhesion was observed on the P(DMAPS)-grafted film surfaces. The P(DMAPS) grafting can further decrease hemolysis and enhance the PRT of the PCL surface With the versatility of surface initiated ATRP and the excellent hemocompatibility of zwitterionic polymer brushes, PCL films with desirable blood properties can be readily tailored to cater to various biomedical applications.