The effect of binder content (aluminum hydroxide) on the textural, acidic, and catalytic properties of nanocrystalline zeolite BEA-based catalysts for the alkylation of benzene with propylene has been studied. It has been shown that increasing binder content increases the volume of mesopores in the sample and decreases the volume of micro- and macropores. Increased binder content in the catalyst primarily results in a decrease in the concentration of weak acid sites, whereas the concentration of strong acid sites changes only slightly. The observed regularity is associated with the reaction of the binder and the zeolite during the preparation of the catalyst, as well as with the formation of new acid sites. It has been found that increasing binder content increases the mechanical strength of the granulated catalyst, but this is accompanied with a decrease of its catalytic activity and stability in the gas-phase alkylation of benzene with propylene. It has been shown that the optimal content of the Al2O3 binder in the catalyst is about 30 wt %. The sample with the optimal binder content has demonstrated a stable on-stream behavior in the liquid-phase reaction that occurred with 99.4 wt % alkylation selectivity, 91.1 wt % cumene selectivity at 100% propylene conversion.