There are various methods for nondestructive imaging of the internal structure of wood. A microwave nondestructive method based on the dielectric properties of a medium is an area of great interest for predicting wood strength in the worldwide wood industry, but the reliable prediction of strength in wood still has not been solved in a satisfying manner. Hence, answering the question of how dielectric properties of the wood are related to strength may improve the efficiency of models for predicting structural performance of wood by microwaves. Relationships were evaluated in this work between dielectric parameters (dielectric constant, loss factor, and loss tangent) and the strength properties of wood. Samples were prepared from fir and oak wood. Dielectric measurement was performed at a frequency of 9.8 GHz using Von Hippel's Transmission Line Method. Wood density and some mechanical properties were then determined according to related ISO standards. The results showed that there were good relationships between the dielectric parameters and the MOR, MOE, IBS, and CS, especially for oak wood. The dielectric parameters were promising to predict wood strength with a high accuracy for oak but not fir, and the dielectric constant had a higher precision degree than the loss tangent and loss factor.