Mordenite (MOR-type zeolite) is a widely used catalyst, in particular for (hydro-) isomerization and alkylation reactions in the petrochemical industry. However, having a one-dimensional micropore system, this material is susceptible to diffusion limitations and deactivation. To circumvent this problem, typically additional (meso)porosity is created by applying dealumination and/or steaming processes. The detailed description of the dealumination process is of crucial importance to understand how mordenite can be modified into an efficient catalyst. In this work, we present for the first time a simulation model to describe the influence of the dealumination process on the structural properties of mordenite. Using kinetic Monte Carlo simulations, dealumination is described as a multiple-step process consisting of the removal of the framework Al as well as the self-healing of silanol nests by Si atoms. The simulation results are in very good agreement with experimental results from 29Si NMR, XRD, and N2 and Ar physisorption. In particular, the simulations confirm the enlargement of the micropores and the creation of mesopores during dealumination.