A series of multifunctional silver-doped titanium dioxide (Ag/TiO₂) nanocomposites with various silver contents were synthesized by the peroxo sol-gel method using TiCl4 as a precursor and H₂O₂ as a peptizing agent. The sol was used to coat a glass substrate, thereby forming a thin film. The antiviral and antibacterial activities of the Ag/TiO₂ films and their use in the photocatalytic degradation of an aqueous solution of methylene blue were investigated. The as-prepared materials were characterized using high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The antiviral and antibacterial activities of the samples were tested against Escherichia coli, the influenza A virus (H1N1), and enterovirus. It was observed that an optimum Ag:TiO₂ weight ratio of 1:100 enabled the highest activity in the photocatalytic degradation of an aqueous solution of methylene blue under irradiation with either ultraviolet or visible light. Moreover, the same composition remarkably exhibited extremely high antibacterial and virucidal effectivenesses greater than 99.99% against E. coli and infectious viruses after illumination with ultraviolet A. The presence of silver on TiO₂ significantly enhanced its photocatalytic activity. Thus, the excellent photocatalytic activities and reusability of the Ag/TiO₂ nanocomposite render it applicable as a coating material for several purposes.