This paper presents the preparation of epoxy/inorganic-nanoparticle hybrid materials synthesized from diglycidyl ether of bisphenol A and colloidal titania (TiO2) with coupling agent, 3-isocyanatopropyltriethoxysilane, and curing agent, hexahydro-4-methylphthalic anhydride, by using a thermal polymerization. The precursor was spin-coated and thermal-cured to form hybrid films. The experimental results showed that the refractive index of hybrid films can be tuned by adding various solid contents of TiO2 to hybrid films. The refractive index at 633 nm increased from 1.450 to 1.639 as the TiO2 content increased from 0 to 50 wt.%. UV–vis analysis showed that the transparency of hybrid films was over 90%. L.a.b. color analysis indicated that the luminance of films was above 95%, and no yellowing was observed. In addition, the hybrid materials exhibited a low hydroscopic property under a high-humidity environment.