An effective method was proposed to prepare low dielectric constant composites based on a hybrid of graphene oxide–POSS and fluoropoly(ether ether ketone) (FPEEK). Through the formation of amide between aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS-NH₂) and oxygen-containing groups (carboxyl groups) on graphene oxide (GO), the covalent functionalization of GO with POSS-NH₂ (POSS-NH₂–GO) hybrid was carried out, which is highly soluble in many organic solvents. The structure of the POSS-NH₂–GO hybrid was confirmed by FT-IR, Raman, XRD, TGA, XPS, and TEM. The POSS-NH₂–GO hybrid was well dispersed within the FPEEK polymer matrix to prepare POSS-NH₂–GO/FPEEK composite films by solution blending. The dielectric constants of the composites decreased with the increasing content of POSS-NH₂–GO hybrid, and a κ value of 2.01 was achieved with the incorporation of the hybrid, only 3.0 wt% could cause a 92.8% high enhancement in Young's modulus.