The effect of alumination on the textural, acidic, and catalytic properties of mesoporous aluminosilicates with an ordered mesopore system has been studied. It has been found that the aluminizing process is accompanied by the incorporation of Al in the aluminosilicate material of the mesopore walls. It has been shown that, in the phenol methylation process, the composition of products over the original (Si/Al = 12.5) and aluminated aluminosilicates (Si/Al = 2.2 and 0.8) is the same, which is indicative of the identical nature of the active sites. Unlike the original mesoporous aluminosilicate, the aluminated materials have exhibited the same level of activity for 4 h. It has been supposed that the stable activity of the aluminated catalysts is caused by the generation of additional acid sites owing to the interaction of the aluminum-enriched material of the mesopore walls with water resulting from the reaction between phenol and methanol.