Differential thermal analysis (DTA) was used to study the crystallization phenomena in Y2O3-Al2O3 fibers formed via a melt extraction process. Such fibers are X-ray amorphous and optically transparent regardless of composition in the as-extracted state but can be crystallized to produce various equilibrium phases that depend on the original composition of the ceramic rods used in the extraction process. The activation energy values were calculated using Kissinger and Augis-Bennett equations by measuring the variation of the peak temperature in the differential thermal patterns with heating rate. X-ray diffractometry analysis was used to determine the phase formation in the fibers crystallized after the DTA scan.