Herein we report an ultrasonic- and photobased synthetic approach for the production of size-selective SrTiO3 nanomaterials that are surface-decorated with Pd nanoparticle cocatalysts for application as photocatalysts for organic dye degradation. Control over the final nanoparticle size was achieved through selection of both reagent concentrations and stoichiometries, allowing for the ability to generate structures with sizes between 50 and 155 nm. Pd nanoparticles were subsequently photochemically deposited onto the surface of the oxide materials to serve as cocatalysts for enhanced reactivity. The materials were fully characterized and then examined for their photocatalytic reactivity, where their overall catalytic properties were controlled by three factors: (i) composition, (ii) size, and (iii) particle surface charge. These studies demonstrate important information that correlates synthetic conditions to final material properties, providing approaches to generate materials with optimal reactivity. Such effects could likely be translated to additional systems for applications beyond photocatalysis, such as energy harvesting, plasmonics, sensing, etc.