In this study the physicochemical properties of titanium dioxide (TiO2) nanoparticles suspended in electrolyte and polyelectrolyte aqueous solutions were investigated The hydrodynamic diameter and the electrokinetic potential of the particles, as indicators of suspension stability, were measured using dynamic light scattering and microelectrophoresis. The research focused on the influence of changes in pH, ionic strength, type/concentration of salts and polyelectrolytes on the stability of nanoparticles (nanoplates and nanospheres) in suspension. It was examined how surface modification with either positively or negatively charged polyelectrolyte affects suspension stability in the presence of monovalent salts. The efficacy of polyelectrolytes as potential stabilizers for nanoparticles, in the context of particle aggregation kinetics, was assessed. It was shown that due to the surface overcharging by the polyelectrolytes, the prepared systems showed exceptional stability, with no aggregation near the isoelectric point. Additionally, it was found that a higher salt concentration is required for nanoparticles aggregation if the polyelectrolyte is adsorbed on the particle surface.