The Chenopodium album plant was collected and the fresh plant extract plays a key role in copper oxide nanoparticle synthesis. The reduction of Cu2+ ions to CuO NPs by aqueous leaf extract of Chenopodium album was visually observed by color variation in the reaction mixture. The UV-visible absorption peak arises from 300-380 nm denote the development of CuO NPs. In our study, the extreme absorption peak seemed at 365 nm directs the individual SPR band for CuO NPs with lesser particle size. In conclusion the copper oxide nanoparticle was synthesized using fresh leaf extract of Chenopodium album. The synthesized nano particle was characterized and confirmed using UV-Visible, FT-IR, XRD, FE-SEM, EDX and SEM mapping analysis, the results showed that CuO Nps were synthesized properly. The in-vitro antibacterial assay depicts the effective antibacterial activity of CuO Nps. These conclude that the further study on CuO Nps helps for the drug development.