A reliable nanocasting method has been developed to synthesize mesoporous hybrids of platinum (Pt) nanoparticles decorating tungsten trioxide (WO3). The process began with modification of the SBA-15 template with carbon polymers and Pt nanoparticles accompanied by adsorption of W(6+), which was then converted into m-Pt-WO3 composites by heat treatment and subsequent template removal. The synthetic strategy can be easily extended to prepare other mesoporous nanohybrids with metal oxide loaded precious metal composites. Comprehensive characterizations suggest that the as-developed m-Pt-WO3 nanohybrid exhibits unique properties with mesoporous structure, excellent crystalline structure, and high surface area. When the photocatalytic properties of m-Pt-WO3 nanohybrids were systematically investigated, it was revealed that the m-Pt-WO3 nanohybrids showed great promise for degrading the organic dye under visible light irradiation, which shows an excellent photocatalytic activity that far exceeded those of pure phase mesoporous WO3 and commercial TiO2 (P25), and was 10-fold more active than that of the bulk Pt-WO3 catalyst. The as-developed synthetic route opens up a new avenue for designing mesoporous hybrid materials for various applications benefiting from the unique porous structure, high surface area, and synergistic effects among constituents.