The modification of chlorinated poly(propylene) (CPP) via graft copolymerization of EHA using ATRgP is reported. The kinetic plot of monomer conversion versus reaction time was found to be linear, which is the typical characteristic of a living controlled polymerization. The grafted copolymers were characterized by means of FT-IR and 1H NMR spectroscopy, GPC, DSC, and TGA. Mechanical properties were also studied by means of UTM and DMA. The stress/strain plot and the tension set properties indicate that the brush-type graft copolymer (CPP-g-PEHA) behaves as a thermoplastic elastomer.