The commercially available V2O5/WO3-TiO2 is a well-known catalyst for selective catalytic reduction (SCR) of NO with NH3. When alkali ions are present in the exhaust (e.g., as impurities such as dust) of a reactor containing commercial V2O5/WO3-TiO2, alkali poisoning occurs, deactivating the catalyst. Consequently, there is substantial interest in the development of better-performing and more durable NH3-SCR catalysts with an improved resistance to alkali deactivation. For the present study, the protonated (H+) form of zeolite Y, HY, was used as a support and acted as buffer zone, leading to trapping (sticking) of foreign alkali poisons in the zeolite pore structure, preventing alkali poisoning of the Fe2O3/HY catalyst. Catalytic tests showed that the Fe2O3/HY retained 100% of its original catalytic reactivity for NH3-SCR reaction even after 1000 μmol Na+ g-1 poisoning. 1000 μmol Na+ g-1 treatment indicates a 26 000-h exposure under an alkaline dust-containing condition. In contrast, upon 1000 μmol Na+ g-1 treatment, severe alkali deactivation occurred for a commercial V2O5/WO3-TiO2. The catalyst activity of Fe2O3/HY remained unchanged because of the intercalation of Na+ in the internal HY zeolite pores that impedes the blocking of Na+ poison to the external active sites of Fe2O3. The findings in this work suggest that the zeolite HY may be revealed as an attractive building block for designing an alkali poisoning-resistant catalyst.