Nanoparticles (NPs) with nonmetallic cores and metallic shells (such as Au, Ag, and Cu) can exhibit improve absorption efficiency due to localized surface plasmon resonance (LSPR), charge density oscillations at the surfaces of these core-shell composite nanoparticles. In this study, the effect of the geometry of TiO2@Ag core-shell composite nanoparticles on their optical absorption properties was theoretically illustrated in the wavelength ranges between the visible and infrared light regions of electromagnetic radiation. These nanostructures were modeled by varying the TiO2 core and Ag shell radii of the composite nanospheres and nanowires. The results indicate that varying the TiO2 core radius and Ag shell thickness can be used to tune the absorption efficiency of these materials from the UV region to the visible or infrared regions of the electromagnetic spectrum. An increase in the absorption efficiency with greater core radii was observed. The absorption efficiency peaks of core-shell nanospheres or nanowires increased with the shell radius. Theoretical modeling based on these results suggest that this nanomaterial can be effectively utilized so that its optical absorption properties can be tuned. These properties could help to synthesize TiO2@Ag core-shell composite NPs for use in environmental applications such as treating contaminated water and in novel future devices.