The formation of zeolite A (LTA) in the presence of tetramethylammonium cations is studied using in situ small angle and wide angle X-ray scattering (SAXS/WAXS) techniques. The SAXS measurements show the formation of homogeneous precursors 10 nm in size prior to the crystallization of LTA which were consumed during the crystallization. The crystal size is estimated by fitting the SAXS patterns with an equation for a cubic particle, and it is revealed that the final crystal size of the LTA depends on the synthesis temperature. However, although such temperature dependence is noted for the final crystal size, the initial precursor particles size appears to be closely similar (ca. 10 nm) irrespective of the synthesis temperature.