In this report, TiO2–SiO2 composite nanoparticles were prepared by the thermal hydrolysis method using titanium tetrachloride and tetraethylorthosilicate as TiO2 and SiO2 precursors, respectively. The prepared nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption/desorption and UV–Vis diffuse reflectance spectroscopy (DRS). The results indicated that, in comparison with pure TiO2, TiO2–SiO2 composite nanoparticles had a higher thermal stability, which prevents phase transformation from anatase to rutile. In addition, the TiO2–SiO2 nanoparticles had a higher specific surface area, larger pore volume, greater band gap energy and smaller crystallite size. Thus, the surface area of TiO2–40% SiO2 composite nanoparticles was about 17 times higher than that of pure TiO2 nanoparticles. The photocatalytic activity of TiO2–SiO2 composite nanoparticles in the photodegradation of C.I. Basic Violet 2 was investigated. The photodegradation rate of Basic Violet 2 using TiO2–40% SiO2 nanoparticles calcined at 600°C was much faster than that using pure TiO2 and Degussa P25 TiO2 by 10.9 and 4.3 times, respectively. The higher photoactivity of the TiO2–SiO2 composite nanoparticles was attributed to their higher surface area, larger pore volume, greater band-gap energy and smaller crystallite size compared with pure TiO2.