Application of microwave energy to wood can increase permeability in order to improve the impregnation of treatments, particularly important in refractory species such as eucalyptus. However, microwave treatment can also affect the physical and mechanical properties of wood. This paper discusses the application of microwave treatments of different intensities to improve impregnability (uptake and retention) and examines the effects on the mechanical properties of eucalyptus wood(Eucalyptus globulus). Microwave treatments significantly improve uptake and retention of the protective agent, especially in the most severe treatment. In contrast, there was a clear decrease inmechanical properties (modulus of elasticity and bending, compression, tension and shear strength) as a function on the energy applied. The effect of microwaves on the properties of wood varies depending on moisture content at the time of treatment.