The presented work demonstrates the preparation of copper nanoparticles (CuNPs) via aqueous leaves extract of Ziziphus mauritiana L (Zm) using hydrazine as a reducing agent. Various parameters such as volume of extract, concentration of hydrazine hydrate, concentration of copper chloride, and pl 1 of the solution were optimized to obtain Ziziphus mauritiana 1. leaves extract derived copper nanoparticles (Zm-CuNPs). Brownish red color was initial indication of the formation of Zm-CuNPs while it was confirmed by surface plasmon resonance (SPR) band at wavelength of 584 nm using ultraviolet-visible (UV-vis) spectroscopy. Synthesized Zm-CuNPs were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AIM, and X-ray diffractometry (XRD). AFM images showed that the particle size of Zm-CuNPs was from 7 to 17 nm with an average size of 11.3 nm. Fabricated sensor (Zm-CuNPs) were used as a colorimetric sensor for the detection of Ag+ at a linear range between 0.67 x 10(-6)- 9.3 x 10(-6) with R-2 value of 0.992. For real water samples, limit of quantification (LOQ) and limit of detection (LOD) for Ag+ was found to be 330 x 10(-9) and 100 x 10(-9) , respectively.