ZnO and Cr-doped ZnO thin films are grown on to glass substrates using reactive electron beam (e-beam) evaporation technique. Variation of structural, morphological, and optical properties with Cr doping is investigated. X-ray diffraction (XRD) studies show that the films are polycrystalline in nature with single phase. Energy dispersive spectroscopy (EDS) results demonstrate that Cr ions are substitutionally incorporated into ZnO. Atomic force microscopy (AFM) reveals that the films present a compact surface and root mean squared (RMS) roughness increased with Cr contents. The optical band gap energy Eg of the films has been determined using Transmission data by spectrophotometer and ellipsometry. The band gap energy found to be decreased with increasing Cr doping concentration. The optical constants (refractive index, extinction coefficient) are calculated using ellipsometry and found to increase with Cr doping concentration.