This study investigates, for the first time, the effects of steam heating of hierarchical porous-structured granular Y zeolite samples and of their subsequent treatment with aqueous nitric and citric acid solutions on the acid properties and porous structure characteristics of the samples. It was demonstrated that acid treatment of a sample not subjected to preliminary steam heating stabilization leads to its decationation, dealumination, and partial amorphization of its crystal lattice. In contrast, acid treatment of a steam-stabilized sample was found to mitigate the lattice destruction.