The present paper reports the synthesis and fabrication of CeO2-Gd2O3-CoO nanocomposite films using metal carboxylates as precursors. The refractive index of the film was found as 1.445538. The crystallinity was confirmed from XRD and the minimum crystallite size calculated was 9 nm. TEM analysis showed the hexagonal crystals where the minimum dimension was obtained as 6 nm. The dimensionality was further confirmed by Particle Size Analyzer. The film was then examined using SEM which revealed highly porous nature of the material. UV-Vis spectrophotometer found the absorption of the film taking place in UV-region and the optical band-gap as determined from Tauc plot was 3.987 eV. The film was used as transmission based opto-electronic humidity sensor. Owing to the highly porous nature of the film, the maximum sensitivity was found as similar to 2.006 mu W%RH, which is showing the quite efficient behavior of the film towards humidity. Response and recovery times were found as 71 s and 86 s respectively, also similar to 91% reproducible results were found while repeating the experiment.