Mesoporous nanocomposites of Pt-reduced graphene oxide (RGO)-layered titanate are synthesized by the reaction of a mixture of exfoliated layered titanate nanosheets, graphene oxide nanosheets, and H2PtCl 6 with NaBH4 to investigate the effect of layered metal oxide nanosheets on the electrocatalyst performance of Pt-RGO nanocomposites. The obtained ternary nanocomposites are composed of a porous stacking assembly of layered titanate/RGO nanosheets with well-dispersed Pt nanocrystals whose particle size becomes smaller with the increase of titanate content. The incorporation of layered titanate nanosheets into the Pt-RGO nanocomposite induces a marked increase of surface area through the frustration of a strong π-π interaction between RGO nanosheets by the intervention of titanate nanosheets. In addition, the incorporation of layered titanate nanosheets gives rise to a remarkable improvement of electrocatalytic activity for oxygen reduction reaction (ORR). Of prime importance is that the present nanocomposites show a more positive onset potential for ORR than commercial Pt/carbon catalysts, underscoring a powerful role of titanate nanosheets in optimizing the electrocatalyst performance of Pt-RGO nanocomposites. This is the first report showing the usefulness of metal oxide nanosheets as an effective additive for enhancing the electrocatalyst performance of platinum nanoparticles. The observed enhancement of electrocatalytic activity upon the addition of titanate nanosheets is attributable to the decrease of Pt crystal size, the increase of surface area, and the increase of surface hydrophilicity. The present findings clearly demonstrate that the incorporation of layered titanate nanosheets is quite effective in improving the electrocatalytic functionality of Pt-RGO nanocomposites.