Cu2+ doped ZnS nanoparticles (Cu/ZnS) were prepared through a modified chemical precipitation method. The nanoparticles were characterized using UV-vis, PL, XRD, XPS, N-2 sorpometry and TEM techniques. The nanoparticles morphology was spherical in shape with a particle size of -11.8 nm and -13.4 nm for bare and Cu2+ doped ZnS, respectively. Upon doping Cu2+ (0-5 mol %) into ZnS, tuning of band gap from 3.93 to 2.72 eV along with a remarkable enhancement in surface area from 89.5-152.7 m(2). g(-1) were successfully achieved. Moreover, Cu2+ act as electron trapping centers, which hinder the recombination of the photogenerated electrons and holes as evidenced from the PL intensity behavior. The photocatalytic experiment by degrading 4-chlorophenol (4-CP) under natural solar radiation indicated that the photodegradation efficiency of Cu2+ doped ZnS nanoparticles increased to 91.2 % compared to 22 % for undoped ZnS nanoparticles. Total organic carbon (TOC) analysis was performed to assess the mineralization ability of the Cu2+ doped ZnS nanoparticles which gave 91.5 % TOC removal. For in-depth understanding of the reasons behind Cu2+ doped ZnS nanoparticles photoreactivity, the revealing of reactive oxidative species (ROS) was achieved through scavenging trapping experiments.