The present invention relates to a process for preparing zeolite crystals having a multimodal particle size distribution, and the sizes of which are between 0.02 μm and 20 μm, said process comprising feeding at least two reactors each with a synthesis gel capable of forming zeolite crystals, carrying out a crystallization reaction, in parallel, in each of the at least two reactors, and mixing the reaction media of the at least two reactors, after the start of at least one of the crystallization reactions.