The thermal stresses in the vicinity of a spherical inclusion within a matrix with different thermal and mechanical properties are analyzed for the condition of linear heat flow and the presence of an interfacial thermal barrier. A numerical example indicates that the existence of such a thermal barrier can have a significant effect on both the magnitude as well as sign of the thermal stresses as the result of disturbance of the temperature distribution due to the inclusion. For the case of perfect thermal contact, the results correspond to those obtained by Tauchert. It is also shown that the presence of an interfacial thermal barrier introduces an inclusion size effect on the magnitude of the thermal stresses, in addition to the direct linear dependence of the stresses on inclusion size, regardless of the existence of a thermal barrier.