Isobutylene synthesis from acetone in the presence of micro-mesoporous MOR zeolites obtained by hydrothermal recrystallization and modified with magnesium acetate by incipient wetness impregnation has been studied. A kinetic study of the reaction has been conducted, and product formation routes have been determined. It has been found that an increase in the mesopore content leads to an increase in the catalyst activity owing to the removal of diffusion restrictions. It has been shown that isobutylene formation occurs on both Lewis and Bronsted acid sites. The modification of the initial aluminosilicates with magnesium has been found to decrease the number and strength of Bronsted acid sites and thereby lead to a decrease in the number of side reactions and an increase in the time-on-stream stability of the catalysts.