The suitability of nanoclay reinforcement for improvement of structural and electrical properties of thermosetting epoxy systems at 10 GHz is investigated via a resonant technique. In recent years, the potential of nanoclay reinforcement to improve mechanical properties and mitigate moisture diffusion in polymer materials has been well documented. Additionally, research has shown that the presence of moisture in polymer systems has a profoundly deleterious effect on relative permittivity and loss tangent of the material. This is especially important for construction or coating of radar protecting structures (radomes), where low permittivity and loss tangent are crucial for radar transparency. Therefore, the addition of nanoclay to polymer composites used in radome applications may prove a feasible method for dielectric and structural performance improvement, and moisture absorption reduction. The relative permittivity and loss tangent of two epoxy resin systems are evaluated as a function of Cloisite 15 nanoclay weight percentage using a split-post dielectric resonator operating at an X-band frequency. Nanoclay content up to 5% by weight is investigated for both systems. The addition of nanoclay did not have a significant effect on the relative permittivity of the material, contributing only up to a 1% decrease (improvement) compared to the neat epoxy. The material loss tangent, however, exhibited a consistent downward trend, with a nearly 13% decrease recorded for the nanoclay content of 5% by weight in the most extreme case. Based on these results, the addition of nanoclay to polymer composite materials used in radome applications has no detrimental effect on the dielectric properties of the material, and as such may prove to be a viable option for improving radome performance and longevity.