In this study, various combinations of TiO2 and SiO2 nanoparticles were prepared using different methods. TiO2 and SiO2 nanoparticles were separately modified by tetraethyl orthosilicate and titanium tetraisopropoxide, respectively. SiO2/TiO2 nanocomposite was synthesized through a two-step sol-gel route. A physical blend of TiO2/SiO2 nanocomposite was also prepared. The nanoparticles were characterized using FTIR spectroscopy, thermal gravimetric analysis, and X-ray diffraction technique. Specific surface area of the nanoparticles was determined using Brunauer, Emmett, and Teller method. The colloidal stability of various nanoparticles was investigated visually and instrumentally in an aqueous media. Photocatalytic activity of nanoparticles was studied through photo-degradation of rhodamine-B dyestuff, in aqueous solutions under UVA irradiation. The results showed improvement of dispersion stability along with the decrease in photocatalytic activity for silica-grafted TiO2-nanoparticles in aqueous solutions compared with the untreated particles. However, titania-grafted SiO2 nanoparticles showed reduced colloidal stability and better photocatalytic activity than their untreated counterparts. The synthesized SiO2/TiO2 nanocomposites revealed the enhanced both photocatalytic activity and colloidal stability among the others.