The effect of fillers, polysulfone and polyetherimide, on the mechanism and kinetics of the thermo-oxidative degradation of a composition based on an epoxy oligomer cured with 4,4'-diaminodiphenyl sulfone which proceeds under heating in the nonisothermal regime is studied. A relationship is revealed between the structure of the composition and the mechanism and kinetic parameters of the process, on one hand, and the chemical nature of the filler, on the other hand. Mechanistic and kinetic features of the nonisothermal degradation of the epoxyamine composition are ascertained by the thermoanalytical method using differential scanning calorimetry. The kinetic parameters of the process are assessed by an analysis of thermokinetic curves in terms of thermokinetic models and the examination of oxidation products. Depending on the filler nature and composition structure, reactions involving bonds of interjunction chains and junctions of the network of the epoxy polymer as well as radical reactions of the active centers of the filler occur in the polymer during thermal oxidation. An increase in the network density and the localization of the filler determine the contribution of the diffusion factor, decrease the rate of thermo-oxidative degradation of interjunction chains, and increase the rate of breakdown of network junctions.