This work is devoted to the study of the composition and structure of thin “spin-on glass” films and xerogels prepared from silica sols containing platinum and palladium compounds, both separately and together. The thickness and concentration distribution of Pt/Pd nanoparticles (NPs) in silica films depending on the concentration of precursors of platinum and palladium in silica sols were determined using the method of X-ray reflectometry. The composition and size of Pt/Pd nanoparticles formed in xerogels and thin films were determined in the nanometer and submicron ranges by means of atomic force and transmission electron microscopy of high resolution as well as by means of X-ray diffraction analysis. It was also determined that bimetallic Pt/Pd nanoparticles possess a common crystal lattice forming clusters with the structure of a mixed alloy type. Highlights Pt/Pd NPs with bimetallic crystal lattices form from TEOS-derived sols doped with Pt and Pd. The size of Pt/Pd bimetallic NPs formed in films is 5–6 nm and of the ones formed in xerogels–10–18 nm. A Pt and Pd concentration gradient is detected in 30–40 nm-thick doped silica films. Pt/Pd crystallites up to 70 nm in size form at the meso level as well.