In this study, oleuropein was isolated from olive leaves by chromatographic method and its structure was elucidated by spectroscopic analyses such as FTIR,H-1-NMR and(13)CNMR. Silver nanoparticles (AgNPs) were synthesized using oleuropein and their antioxidant activity was investigated using DPPH, ABTS(center dot+), and FRAP assays. The AgNPs were characterized by UV-Vis, FT-IR, XRD, and SEM analyses. The absorption peak at 450 nm in UV-Vis spectrum confirmed the AgNPs formation. Scanning electron microscope (SEM) identified the formation of spherical-shaped nanoparticles with the average size of 71 nm. Rietveld analysis was carried out by X-ray diffraction data with High Score Plus software. XRD with2 theta degrees at 38.1 degrees, 44.3 degrees, 64.4 degrees and 77.4 degrees can be assigned to the (111), (200), (220) and (311) Bragg's reflections of the face-centered cubic crystalline structure. Biosynthetic nanoparticles revealed more inhibitory effect (5.22, IC50,mu g/mL) against ABTS(center dot+)than standard BHT (7.03, IC50,mu g/mL).