Experimental data concerning the kinetics of mass crystallization of struvite during the process of magnesium ion removal from water with the use of ammonium dihydrogenphosphate, NH4H2PO4 , addition under alkaline conditions are presented. The tests were carried out in a continuous laboratory DTM MSMPR crystallizer with internal circulation of suspension (T = 298 K). The influence of concentration of Mg2+ ions in the raw material, pH of the process environment, and residence time of suspension on the nucleation and growth rates of struvite crystals was established. Kinetic parameters were evaluated from the crystal size distributions using selected size-dependent growth (SDG) models.