The synthesis of metal nanoparticles by a green method is eco-friendly, nontoxic and few benefits to the growing fields of research used inhibit bacteria and cancer growth over the recent years. In this study, CuO NPs are synthesized through Euphorbia hirta leaf extract. Formation of CuO NPs was confirmed by SPR peak at UV spectrum. FTIR identified functional groups are responsible for reduction and stabilization, GC–MS, phytochemicals present in the Euphorbia hirta extract accountable for synthesizing CuO NPs. XRD confirmed crystalline nature, SEM and TEM confirmed size and spherical morphology. Furthermore, CuO NPs effective antibacterial activity to inhibit pathogens, strong biological activities regarding antioxidant activity and anti-inflammatory activity and excellent anticancer activity against the Ht-29 cell line. Also, good catalyst for the effective degradation of methylene blue. The present study suggests that biosynthesized CuO NPs through an extract from Euphorbia hirta may be used for therapeutic application in future clinical studies. [ABSTRACT FROM AUTHOR]