Nano-crystalline iridium oxide thin films were obtained by spray pyrolysis technique onto preheated glass substrates. X-ray diffraction reveals that, IrO2 thin films were polycrystalline in the rutile structure with primitive tetragonal lattice and its preferential orientation were along the and directions. X-ray diffraction line profile analysis (XRDLPA) was used to assign microstructure and crystal imperfections of IrO2 thin films. Some important parameters such as crystallite size, microstrain, average residual stress, number of crystallite/cm2 and dislocation density were studied. The effect of deposition temperatures and solution concentrations on the microstructural and crystal defects were discussed. All estimated values were found to be dependent upon the growth parameters. Mott parameters, trapping state energy and potential barrier were investigated and studied for a defined thin film sample. This sample was selected because it has the suitable conditions for electrochromic applications.