In this research study, the sustainable and eco-friendly green synthesis report on the use of plant extract alternate to chemicals was discussed. The Catharanthus roseus extract was used as a natural reagent to synthesize nanoparticles a brief discussion on the usage of plant extract were also summarized.Copper oxide nanoparticles (NPs) were successfully prepared using a simple way involving the combination reaction between copper nitrate and leaf extract. The synthesis under leaf extract response played an important role and led to the formation of copper oxide NPs of different size and shapes. The catalyst was characterized by XRD, FTIR, UV–Vis–DRS, PL, SEM with EDX and TEM analysis. The crystalline structure and phase identification was examined using XRD analysis, The XRD results revealed formation of pure phase without any post annealing. Formation of the metal oxygen bond of CuO nanoparticles was confirmed by Fourier transform infrared spectroscopy (FTIR). The surface morphology of the CuO nanoparticles depicted nanorods and the size difference depends upon the method of synthesis. EDX analysis confirmed the phase-purity of the as synthesized nanoparticles. UV-Vis DRS of the as obtained nanorods exhibited the absorbance in the visible region. Photocatalytic activities of the CuO nanoparticles were evaluated based on photodegradation of rose Bengal under UV light irradiation. The results suggested that the nanocatalyst CuO has potential applications as an efficient catalytic material with high efficiency for the photocatalytic degradation of organic pollutants in aqueous solution under UV light irradiation.