Undoped thin films of ZnO were prepared over glass substrates using a simple chemical spray pyrolysis process. The solution of aqueous ‘Zinc acetate dehydrate’ was used as precursor and sprayed over preheated glass substrate at 400 °C. The concentration of solution changed from 0.2M to 1 M with the step of 0.2 and its impact on structural, morphological and optical properties has been studied with the help of XRD, SEM, UV-Vis Spectroscopy and four-probe technique. The films are polycrystallines, have a hexagonal wurtzite structures, and have a preferred orientation in the (002) plane. SEM analysis indicates the dependency of film morphology on precursor concentration. Optical Transmittance decreases with increasing precursor concentration. Maximum optical transmittance reaches up to 51% with film obtained from 0.2M concentration. Decreasing band gap values from 3.18 eV to 3.04 eV are noted as carrier concentration increases with precursor concentration.