During the olive oil production process, large amounts of a solid residue called olive pomace is produced. It is rich in polyphenols, compounds with proven antioxidant activity. The aim of this research was to develope the process of biogenic synthesis of selenium nanoparticles using olive pomace extract (OPE) as a natural coating agent that will potentially have a synergistic antioxidant effect with selenium. Selenium as the component of glutathione peroxidase has an indirect antioxidant effect, while polyphenols have a direct effect on scavenging free radicals, are strong reducing agents and chelate metals. Optimized synthesis of SeNPs has been conducted using different concentrations of OPE. Nanoparticle size distribution, stability and zeta potential was determined by DLS analysis. Antioxidant activity was examined by ABTS and Folin-Ciocalteu methods. Chemical synthesis of SeNPs using polyvinylpyrrolidone was used as a positive control of the synthetic process.. Two significant fractions of SeNPs with an average size of 35 and 215 nm were successfully synthesized by biogenic synthesis, which showed a certain degree of instability in storage stability tests. Analysis of zeta potential showed that the electrostatic repulsion between the synthesized SeNPs was satisfying (approx. -22,5 mV). Unlike chemically synthesized SeNPs, biogenically synthesized SeNPs show significant antioxidant activity in terms of direct scavenging of free radicals and overall reduction potential. The best results were obtained for the sample prepared with 0.862 g/L OPE while further increase of OPE concentration (above 0.862 g/L) had no effect on antioxidant potential of SeNPs. The results of this research significantly contribute to current knowledge on possibilities of using olive pomace extract in the development of nanonutraceuticals, more precisely, the possibilities of using these extracts as natural functional coating agents in formulation of metal nanoparticles.