The crystallization behavior and kinetics of fly ash-based glasses were investigated by using DTA and SEM techniques. The crystal growth activation energies were determined by using the Kissinger and Matusita-Sakka equations as 200 and 283 kJ/mol, respectively. The Avrami exponent (n) was calculated by means of Augis-Bennet and Ozawa equations. Calculated values indicated that the crystallization mechanism was a three dimensional bulk process. This result is in well agreement with the cross-sectional SEM investigations.