The reduction of N2O to N2 on iron oxide under transient conditions was studied in the temperature range of 270–340°C. Six different models were used to simulate the experimental data. The conventional second-order reaction between gas phase N2O and surface oxygen vacancies failed to describe the dynamic experiments. Upon introducing linear or exponential distributions of the second-order surface reaction rate constant in function of the degree of reduction of the surface, satisfactory fittings to the experiment could not be achieved either. It was necessary to take into account subsurface oxygen diffusion to describe the low rates of reaction measured at low degrees of reduction of the catalyst. The combination of subsurface oxygen diffusion with a linear activity distribution for the surface reaction provided a good description of the transient N2O reduction. Finally, the surface reaction rate constant as well as the diffusion coefficient of oxygen in iron oxide could be fitted with the Arrhenius law.