The cure behaviors and toughness properties of triglycidyl p-aminophenol/bisphenol F diglycidylether resin system with 4, 4-diaminodiphenylsulfone hardener were studied with the inclusion of polyethersulfone (PES). The cure kinetics of epoxy blends were investigated in both dynamic and isothermal conditions by differential scanning calorimetry (DSC). In dynamic experiments, the activation energy was evaluated by Ozawa and Kissinger’s equations at different heating rates (2~40 °C/min). Isothermal DSC data at different temperatures (160~220 °C) are fitted to an autocatalytic Kamal kinetic model. The tensile, flexural, and fracture toughness of the epoxy blends were investigated by taking into account their morphological features, which were influenced by the PES contents. Consequently, the results obtained from cure behavior studies further indicated that the degree of cure, rate of cure, and activation energy of the epoxy resins were not largely affected by the PES inclusion, while fracture toughness values of them increased with the PES content.