A green synthesis method of silver nanoparticles (AgNPs) using Centaurea virgata Lam. extract and the isolated compound eupatorin was investigated in this study. Ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM)/energy-dispersive X-ray (EDX) spectroscopy, thermal gravimetric analysis, X-ray diffraction analysis and zeta potential were used for characterization of AgNPs. The UV-Vis spectrum exhibited a characteristic absorption band at 420 nm for monodisperse nanoparticles. FTIR measurements also proved the formation. X-ray diffraction patterns showed peaks at (110) and (112), which are characteristic for hexagonal crystals and also showed peaks at (111), (200) and (240), which are characteristic for orthorhombic crystals. The TEM images of AgNPs show that the morphology of AgNPs was predominantly spherical. Obtained AgNPs were highly stable according to the zeta potential values. The nitric oxide scavenging activity, which is also related to anticancer activity, of AgNPs was evaluated. It can be concluded that C. virgata Lam. extract and eupatorin can be used as a reducing agent for potential antioxidant AgNP formation.