Thermal behavior of oil palm fiber-reinforced phenol-formaldehyde (PF) resins with different chemical treatments were analyzed using Differential Scanning Calorimeter (DSC). A well-defined peak of crystallization was observed in all the samples. However, in one of them a second exothermic peak also emerged, which indicates some structural changes at high temperature. Crystallization kinetics has been studied in terms of activation energy of crystallization, dimensionality of growth and stability using various recent theories developed for nonisothermal crystallization. The results indicate the surface nucleation and crystallization through one-dimensional growth. Thermal stability of PF composites increases after chemical treatment, and is maximum for resin treated with peroxide PF composite in comparison to fiber-treated PF composites.