In this work, Titanium dioxide (TiO2) thin films were prepared by atomic layer deposition (ALD). The effect of different substrates on the structural and optical properties of TiO2 thin films was studied. The prepared films were characterized by X - Ray diffraction (XRD) method, reflectance spectroscopy, Photoluminescence (PL) spectroscopy, Field Effect Scanning Electron Microscopy (FESEM) and Energy Dispersive X - Ray (EDX). The XRD results show that the anatase and rutile mixed crystalline TiO2 structure for each substrate.