This invention presents methods for tailoring the size and morphology of zeolite SSZ-13 (CHA type) crystals through the use of modifiers and manipulation of synthesis parameters, such as the selection of the silica source. The modifiers can influence the rate of crystal growth and/or serve as colloidal stabilizers to impede the aggregation of aluminosilicate precursors, thereby resulting in the formation of small crystals with sizes less than 500 nm. Conversely, modifiers may also enhance crystal growth, resulting in the formation of crystals with sizes that exceed 10 microns.