Fabricating elastomeric materials is one of the most important branches in current nanotechnology and composite science. The macroscopic properties of the elastomers can be modified by adding fillers through changing the types and degrees of crosslinkings. In this study, copolymer-grafted multiwalled carbon nanotube composite thermoplastic elastomers (CTPEs) have been designed, in which the grafted poly( n-butyl acrylate- co-methyl methacrylate) (P(BA- co-MMA)) random copolymers behave as the soft elastomer, and the homogeneously and discretely dispersed multiwalled carbon nanotubes (MWCNTs) of low amounts provide additional physical crosslinkings, which significantly enhance the mechanical properties of the composite elastomers, including high strain-hardening modulus and much improved elastic recovery. This design concept opens a window to produce high-performance strong composite thermoplastic elastomeric materials from soft ones through the incorporation of rigid fillers of low amounts by a grafting strategy.