Kinetics of isothermal crystallization of butter oil (BO) and interesterified butter oil (IEBO) with gamma-linolenic acid (GLA; C_18:3 ω-6) at 10 °C were evaluated by applying Avrami equation. Differential Scanning Calorimeter (DSC) analysis of Avrami parameters revealed significant differences (P < 0.05) between BO and IEBO samples obtained at 1, 8, and 24 h of interesterification. Results of crystallization rate constant (k), Avrami exponent (n), and half-time of crystallization (t_1/2) indicated different crystallization mechanisms for BO and IEBO samples. BO illustrated the lowest (P < 0.05) induction time of nucleation with a value of 8.93 min corresponding to its high peak melting temperature (T_{p < /sub>) of 30.54 °C which was converse to IEBO samples. The results were ascribed to alteration (P < 0.05) of fatty acids (FAs) composition of IEBO occurred by lipase-catalyzed acidolysis of BO and GLA.}