Adding noble metals to TiO₂ and CeO₂ creates perspective plasmonic nanocomposites with high activity in the photodegradation of pathogenic microorganisms and organic contaminates. Nanocomposites based on TiO₂ and CeO₂ doped with Ag, Au, Pt, and Pd were synthesized by a sol–gel process using titanium tetraisopropoxide (TTIP) and cerium nitrate as the starting materials. The results of the addition of noble metals of different concentrations on the structural, morphological, and thermal behavior were considered. The formation of a tetragonal crystal lattice of TiO₂ (anatase) and a cubic lattice of CeO₂ was proved by the X-ray phase analysis method. It was stated that the injection of precious metals into the initial solutions leads to a change in the parameters of the crystal lattice and the size (21.8–6.5 nm) of the crystallites (CSR) of nanosized oxides. From the SEM–EDS results, it was evident that the doped nanoparticles aggregated in clusters of different sizes in the host matrix compared to initial oxides. Analysis of the crystal lattice parameters of oxides and the size of cations of by-products allowed us to make assumptions about the double fixation mechanism of precious metals by the phases of titanium and cerium oxides. Thermogravimetric studies proved the decomposition of TTIP at T ~ 230 °C and the anatase structure formation in the temperature range of 420–480 °C depending on the nature of the doping metal. The cerium-containing system is characterized by the gradual high-temperature formation (460–870 °C) of CeO₂ & Pt and (600–870 °C) of CeO₂ & Pd structures and the low-temperature formation (~ 300 °C) of the CeO₂ & Au structure. EDS spectra indicate the composition of nanostructures in addition to the main elements O, Ti or Ce, relics of starting materials, while the determination of precious metals is complicated for spraying samples due to their low content (0.5–6.0 wt.%) and due to the use of precious metals (Au:Pd).