The evolution of the acid–base properties of the surface of zinc oxide powders during mechanical grinding in an attritor is studied. The study is performed using the methods of the adsorption of acid–base indicators and X-ray photoelectron spectroscopy. Correlations between the results obtained by these methods are established. It is shown that a monotonic decrease in the particle size of ZnO powders is accompanied by a nonmonotonic change in the surface acid–base properties.