In order to investigate the influence of erbium (Er) content on morphological, structural and optical properties of ZnO films, both undoped and Er doped ZnO films were prepared by sol gel method using spin coating technique. Surface properties of these films were analyzed by scanning electron microscopy (SEM). It was clearly observed from SEM micrographs that surface of 1% Er-doped ZnO film made up of nanorods. X-ray diffraction (XRD) spectra showed that all the films were crystallized in the hexagonal wurtzite phase with a preferential orientation along the c-axis. The crystalline quality of undoped ZnO film deteriorated with the erbium. At the visible region, the average optical transmittance values of all the films are greater than 84%. The values of absorption band edge were determined from plot of the first derivative of the optical transmittance versus wavelengths. The optical constants of the films were calculated using transmittance and reflectance spectra. Hall Effect measurements reveal that the prepared films have n-type conductivity and their electrical resistivity's has increased significantly with Er content.