Nanoparticles of a polyelectrolyte complex of natural polysaccharides chitosan and kappa-carrageenan have been obtained as potential biocompatible delivery systems for the glycopeptide antibiotic vancomycin. Colloidal and chemical characteristics of the complex particles, namely, diameter (130÷180 nm) and electrokinetic potential, have been determined. The nanometer size range of the initial particles of the polyelectrolyte complexes and complexes with immobilized vancomycin has been confirmed by scanning electron microscopy. It has been shown that with the addition of carrageenan to the chitosan solution, a decrease in the ζ-potential of the particles is observed due to the electrostatic interaction of the polyelectrolytes. Immobilization of vancomycin on the particles of the complex does not lead to significant changes in their characteristics. In the IR spectra of the product of the interaction of the complex with vancomycin, a band attributed to deformation vibrations of N-H bonds in peptides and a band corresponding to phenolic hydroxyls of vancomycin have been detected, which indicates immobilization of the antibiotic on the particles of the complexes. Vancomycin release from polymer carriers was monitored spectrophotometrically in the UV range using water and TRIS buffer simulating physiological fluids of the human body as receiving media. The study of the optical characteristics of vancomycin solutions showed the presence of a characteristic absorption peak at a wavelength of 280 nm, the position of which is preserved when adding additives of the polyelectrolyte complex to the solution. The limits of detection and quantitative determination of the drug were determined. It was found that when TRIS was used as a receiving medium, the rate of vancomycin release from the polyelectrolyte complex was significantly slower than in an aqueous medium. Analysis of the mechanism of release of the biologically active substance from nanoparticles, carried out within the framework of the Korsmeyer-Peppas mode drug release mathematical model, showed that the process of vancomycin diffusion is accompanied by the destruction of the polymer carrier.