A novel copper phthalocyanine-grafted graphene oxide (CuPc-g-GO) nanohybrid was prepared via in situ polymerization. Isophorone diisocyanate (IPDI) and 3-aminophenoxyphthalonitrile were employed to functionalize GO with phthalonitrile moieties (GO-IPDI-CN), which was subsequently polymerized with 1,3,5-tri-(3,4-dicyanophenoxy) benzene and CuCl, forming the copper phthalocyanine between the sheets of GO. The CuPc-g-GO and the intermediates were characterized by FTIR, TGA, DSC, XPS, SEM, UV-Vis, XRD, and AFM. The results suggested that CuPc was successfully grafted on the surface of GO, and the GO was completely exfoliated after the grafting of the CuPc. And the formation of the nanohybrids effectively enhanced the dielectric constant of CuPc, which was as high as 9.04 at 100 Hz, with an increment of 116 %, when the mass fraction of GO-IPDI-CN was 10 wt%.