Mixed metal oxide (MMO) nanostructures co-doped uniformly by carbon and nitrogen are synthesized for the first time by annealing a terephthalate-intercalated layered double hydroxide (LDH) under ammonia gas flow. The interlayer gallery of LDH allows effective access of NH3 and the carbon source to its crystal lattice for a uniform nitrogen and carbon doping. Such co-doped MMO exhibit significantly red-shifted absorption spectra to visible light region relative to pure MMO. Photoelectrochemical water oxidation and incident-photon-to-current-conversion efficiency of LDH-derived photocatalysts demonstrate that all the visible light absorption caused by the anion doping contributes to the photocatalytic activity over the entire absorbed wavelength range of <610 nm. Density functional theory calculations of electronic structures are performed to elucidate the possibility of bandgap narrowing upon nitrogen and carbon co-doping on MMO structures.