The aim of this study is to analyze the photocatalytic dye degradation efficacy of ZnO/g-C3N4/Ag composite thin films prepared using a simple jet nebulizer spray pyrolysis technique. The XRD results confirm the presence of phases related to silver and graphitic carbon nitride in addition to the host ZnO wurzite structure. The photocatalytic studies show that the addition of Ag and g-C3N4 remarkably improves the photocatalytic efficiency of ZnO. The ZnO/g-C3N4/Ag thin film causes 96 and 99% decomposition of Methylene Blue (MB) and Malachite Green (MG) dye molecules, respectively. The mineralization of the dyes is confirmed by COD measurements. To find the optimum operating pH of the dye, the point of zero charge and the pH corresponding to the maximum surface negative charge of ZnO/g-C3N4/Ag film are found out experimentally. The possible mechanism and reasons for the enhanced photocatalytic activity of the ZnO/g-C3N4/Ag thin films are discussed with appropriate evidences and related literature.