<p>A stable (ζ-potential of +56 mV) aluminum oxyhydroxide (AlOOH) hydrosol was obtained. Its dispersed phase consisted of plate-like particles with a pseudo-boehmite structure. Electrophoretic light scattering, FTIR and UV—Vis spectroscopy were used to study surface modification of the nanoparticles with chlorogenic acid (CGA). During the interaction, the isoelectric point shifted towards a less alkaline region, and a decrease in the ζ-potential of the hybrid particles and the pH of the medium were observed. These changes are related to a partial neutralization of the surface hydroxy and carboxy groups and a release of protons from the surface into the dispersion medium. Adsorption of CGA onto the AlOOH surface occurs instantaneously and is accompanied by the transition of the acid into its deprotonated forms (HCGA²⁻/CGA³⁻), despite the near-neutral environment. Binding occurs both <i>via</i> the carboxy groups of the quinic acid moiety and the phenolic hydroxy groups of the caffeic acid moiety. The absence of desorption in the presence of KCl and negligible desorption in the presence of K₂SO₄ point to a strong binding affinity of CGA to the nanoparticle surface. The obtained results confirm that AlOOH nanoparticles are highly promising objects for use as carriers for the immobilization of phenolic acids, which is demonstrated by considering CGA as a representative example.</p>