Chemically modified copper phthalocyanine (CuPc) oligomer with active vinyl groups was successfully bonded to poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) backbone via free radical graft reaction in solution. Improvement of the dispersibility of CuPc oligomer in polymer matrix was confirmed by TEM-observed morphologies. The size of CuPc particulates in the polymer matrix is in the range of 60-120 nm. This nanocomposite (with 25 wt % CuPc) is very flexible with an elastic modulus of 912 MPa, which is nearly the same as that of the polymer matrix, and presents a breakdown field of 37.7 V/mum, while for the blend of P(VDF-TrFE) and CuPc oligomer, it is 29.7 V/mum. The dielectric constant reaches about 100 at 100 Hz and room temperature, representing a more than 6 times increase compared with the matrix. The grafted nanocomposite exhibits a weaker dielectric dispersion in comparison with the blend of P(VDF-TrFE) and CuPc oligomer, particularly at low-frequency range. The low-frequency dielectric dispersion can be attributed to the Maxwell-Wagner-Sillars polarization mechanism.