The present investigation describes the preparation and characterization of novel biodegradable nanoparticles based on complexation of poly-gamma-glutamic acid (y-PGA) with bivalent lead ions. The prepared nanosystems were stable in aqueous media at low pH, neutral and mild alkaline conditions. The solubility and size of these nanoparticles in the dried and swollen states will be described and discussed. The correlation of size of particles, pH of the solutions, concentration and the ratio of compound polyelectrolytes have been studied. It was found, that the size of individual particles was in the range of 40-100 nm measured by TEM. The low and high pH values in mixtures with high concentrations of γ-PGA and Pb2+ ions favored the growth of large complexes. The y-PGA nanoparticles, which are from a biodegradable biomaterial with high flocculating and heavy metal binding activity, may be useful for various water treatment applications in aqueous media.