Spherical mesoporous silica particles with entrapped metal nanoparticles are synthesized from a onestep aerosol-assisted self-assembly process using sols of an alkoxysilane, ethanol, surfactant, water, HCl, and metal precursors (e.g., salts or complexes). Utilizing nitrogen as a carrier gas, the sol is sent through an atomizer, producing aerosol droplets, which are passed through a tubular furnace heated to 400 °C. Solvent evaporation from the droplets enriches the nonvolatile components and results in the coassembly of silicate and surfactant into 3-dimensional mesostructures with incorporated metal precursors. Lamellar, cubic, and hexagonal mesostructures are achieved by using different surfactants. Subsequent calcination of the surfactant and reduction of the metal result in spherical mesostructured porous silica particles with supported metal nanoparticles. Nitrogen sorption techniques, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction are used to characterize the particles. Mesoporous silica particles with 0.5% Pd are tested as a catalyst in the hydrodechlorination reaction of 1,2-dichloroethane and exhibit ∼100% conversion above 350 °C and ∼100% ethylene selectivity, demonstrating the potential of such nanocomposites as catalysts.