Nanocomposite thin film containing TiO 2 nanoparticles in polymethyl methacrylate (PMMA) is a new class of potential materials for optoelectronic applications. Among the various processing techniques for these nanocomposites, in situ sol-gel process is well known to be versatile as it enables control of the inorganic-organic interaction at various molecular, nanometer and micrometer scales. However, the resulting TiO 2 phase is largely amorphous, as a consequence of the relatively low processing temperatures. Therefore, the current research is aimed at enhancing the nanocrystallinity of TiO 2 nanoparticles in nanocomposites. For this purpose, pre-hydrothermal treatment was carried on the inorganic sols. The nanocrystallinity degree of the resulting TiO 2 nanoparticles was studied by XRD and FTIR. The studies showed that the nanocrystallinity of TiO 2 nanoparticles synthesized from the inorganic sol can be enhanced significantly by the pre-hydrothermal treatment, as a result of the completion of hydrolysis stage during sol-gel process.