The effect of crystallization parameters on the properties of nanocrystalline zeolites Y has been studied to optimize the synthesis conditions. Zeolites Y are prepared by the three-stage hydrothermal crystallization with a gradual rise in synthesis temperature from room temperature to 60A degrees C using the Na2O/SiO2 ratio in the reaction mixture and the number and duration of individual synthesis stages as variable synthesis parameters. It has been shown that an increase in the Na2O/SiO2 molar ratio in the reaction mixture above 9.6 leads to a change in the crystallization selectivity and causes formation of zeolite X with a crystal size of 200 nm as a crystalline product. An increase in the duration of the synthesis stage at 60A degrees C is accompanied by increase in the crystal size and entails formation of an analcime impurity phase. A decrease in the duration of reaction mixture aging stages at 25 and 38A degrees C leads to an increase in the zeolite Y nanocrystal sizes and a decrease in the crystalline product yield. It has been found that a pure zeolite Y phase with a nanocrystal size of 320-350 nm and a SiO2/Al2O3 ratio of 3.6-4.2 is formed during the three-stage synthesis from a (7.2-9.6)Na2O center dot Al2O3 center dot 14.4 SiO2 center dot 290 H2O reaction mixture with a yield of 0.60-0.88 g/g of reaction mixture.