Ordered mesoporous carbon/iron oxide composites were prepared by cooperative self-assembly of poly(t-butyl acrylate)-block-polyacrylonitrile (PtBA-b-PAN), which contains both a carbon precursor block and a porogen block, and phenol-functionalized iron oxide nanoparticles (NPs). Because of the selective hydrogen bonding between the phenol-functionalized iron oxide NPs and PAN, the NPs were preferentially dispersed in the PAN domain and subsequently within the mesoporous carbon framework. Ordered mesoporous carbon nanocomposites with Fe2O3 NPs mass loadings as high as 30 wt % were obtained upon carbonization at the block copolymer composites at 700 °C. The morphology of the mesoporous composites was studied using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N2 adsorption. The results confirmed high-fidelity preservation of morphology of the NP-doped block copolymer composites in the mesoporous carbon composites. The electrochemical performance of the mesoporous composite films improved significantly upon the addition of iron oxide NPs. The specific capacitance (Cg) of neat mesopororous carbon films prepared from PtBA-b-PAN was 153 F/g at a current density of 0.5 A/g, whereas films containing 16 and 30 wt % Fe2O3 present as well-dispersed NPs within the mesoporous carbon framework exhibited capacitances of 204 and 235 F/g, respectively. The well-defined mesoporous in the template carbon structure together with high loadings of iron oxide nanoparticles are promising for use in supercapacitor applications.