Polyhedral oligomeric silsesquioxane-functionalized graphene oxide (POSS-GO) was synthesized by the amidation reaction and applied to an organic coating to provide corrosion protection to hot-dip-galvanized steel. The good dispersion of the functionalized graphene oxide in an organic solvent was confirmed. The completeness and barrier property of the POSS-GO composite coating were better than those of additive-free and pure GO. Compared with the pure GO-containing coating, the corrosion rate of the POSS-GO-containing coating decreased by 32% to 0.49 mm/year. Thus, the corrosion resistance was significantly enhanced.