The effect of reactive diluent on the thermal degradation kinetics of epoxy-anhydride resins has been studied by thermogravimetry in both isothermal and non-isothermal conditions. It was found that the kinetics of thermal degradation can be described well by a simple reaction order model. The addition of reactive diluent increases the apparent activation energy and the kinetic exponent. A difference was also observed between the set of kinetic parameters obtained by kinetic analysis of isothermal and non-isothermal data. Such behavior indicates a more complex mechanism of thermal degradation of epoxy resin.