The automated jet nebulizer spray pyrolysis technique was exploiting to deposit ZnO thin films over the glass substrates maintained at temperature 300oC. The effect of volume of the precursor solution over the structural, surface morphological, compositional, optical, electrical and gas sensing properties of ZnO thin films were studied. X-ray diffraction results show that the deposited films are having hexagonal structure with (002) as high preferential orientation plane. SEM studies shows uniformly distributed hexagonal shaped crystals over the surface. Photoluminescence band edge emission at 384 nm, indicates the high crystal quality. From the optical measurements, it is found that the prepared films have a maximum transmittance greater than 90% and direct band gap energy below 3.36 eV. The gas sensing characteristics of the fabricated material was studied by exposing it to ammonia gas. The gas sensitivity, response time and recovery time are studied and reported.