The presence of pollutants such as harmful heavy metals in aqueous system is currently one of the largest environmental problems. Due to unmanaged discharge from numerous industries, this system is a serious problem in the major cities of developing nations. Due to the adverse effects on the environment and potential to cause cancer in humans, these contaminants are anticipated to require special consideration. Pollution clearance is a difficult problem that needs to be tackled if adverse effects on people and the environment are to be avoided or minimized. The main objective of this present research is to synthesize zinc oxide nanoiparticles (ZnO-NPs) from Nyctanthus arbor-tristis flower in a safe, non-toxic, and ecologically friendly manner. The adsorption of U(VI), Pb(II), Cr(VI) and Cd(II) ions from aqueous solutions by Nyctanthus arbor-tristis flower extract was investigated under laboratory conditions to assess its potential in removing these metal ions. The impacts of the experimental factors, such as ZnO-NPs dosage, solution pH, and contact time, were investigated. The study shows that the majority of the toxic metal ions can be adsorbed from the solution in a relatively short duration of time under ambient conditions. The adsorption behavior of toxic metal ions onto the ZnO-NPs was analyzed with Freundlich as well as Langmuir rate equations and the results were supported by the pseudo-second-order kinetic models. The study provides a safe, non-toxic, and eco-friendly green synthesis method and also demonstrated excellent performance of the synthesized ZnO-NPs.