Zeolite crystals are often subjected to different post-synthetic chemical treatments prior to being used in catalytic or separation processes. We highlight a novel non-chemical post-synthetic approach to overcome diffusion limitations in zeolite catalysts and boost their catalytic activity by applying a constant pressure to downsize micron-sized zeolite crystals to sub-micron-sized particles. The method is highlighted by treating a ZSM-5 with hydraulic pressure. The physicochemical characterization of the resulting material shows a substantial reduction in the size of the crystals without altering their native properties (crystallinity, porosity, acidity). ZSM-5 crystals processed in such a way exhibit improved catalytic activity in the Methanol-to-Olefins (MTO) reaction, where the cumulative amount of methanol converted is two and a half times greater than their parent. This is ascribed to the enhanced molecular diffusion of the pressure-treated crystals, which is supported by breakthrough curve analysis.