Nanotechnology and nanosciences are emerging as new fast-growing fields due to their unique characteristics and phenomenal properties. In this study, we synthesized zinc oxide nanoparticles (ZnO NPs) by using leaf extract of Carthamus oxycantha. The morphological features of synthesized nanoparticles were evaluated by standard characterization techniques. The synthesized nanoparticles were irregular and hexagonal, and their average size was 11nm, as revealed by Scanning Electron Microscopy (SEM) and X-ray crystallography (XRD). Flavonoids and other phytochemicals were found to be capping metabolites for the nanoparticles. The synthesized nanoparticles showed significant inhibition of bacterial and fungal strains. The cytotoxicity assay showed 80% mortality of the marine larvae Artemia salina at a sample concentration of 40μg/ml. The crystallized ZnO NPs exhibited toxicity against MFC-7 breast cancer cells and displayed higher antioxidants profile i.e. free radical scavenging activity (76.824±1.22%), total reducing power (90.21±1.12μgAAE/mg), total antioxidant potential (72.936±0.93 μgAAE/mg). Quantity of 80 μg/ml of ZnO NPs resulted in 11.69±0.41% hemolysis against human red blood cells. Due to their potent biological activities, ZnO NPs synthesized from the leaf extract of Carthamus oxycantha could be used efficiently in transdisciplinary research in the future.