The effect of acid treatment on the physical and chemical characteristics of BEA zeolite, as well as the catalytic activity of the Fe-BEA catalyst for N2O reduction under NH3-selective catalytic reduction (NH3-SCR) conditions, was examined. The acid treatment caused dealumination of BEA and enrichment of the silanol groups on vacant Tsites and the Brønsted acid sites. As the acid treatment time increased, the silanol groups and the weak acid sites in BEA also increased. Because the weak acid sites behave as anchoring sites for Fe ions, the catalytic activity also increased as the treatment time increased. However, extended exposure of BEA to acid decreased the catalytic activity of the Fe-BEA catalyst somewhat, and decreased the silanol groups and weak acid sites. The catalytic activity and the amount of weak acid sites were well correlated with the BEA acid treatment time.