The diffusion of oxygen in UO2+α was measured between 600° and 1100°C. Samples with initial O/U values 2.08 and 2.04 were reduced in hydrogen; reduction was monitored continuously by electrical conductivity measurements. The relation between total conductivity and average O/U ratio was derived, and the diffusion coefficients were obtained. The validity of the electrical conductivity vs O/U relation was checked by measuring weight loss during reduction. Diffusion‐controlled kinetics were confirmed by oxygen gradient measurements. The oxygen chemical diffusion coefficient is given by D= 0.5 exp ‐ This equation agrees with previously determined values of the oxygen chemical diffusion coefficient of UO2+α.