In this study, the effect of strand diameters on the dynamic behavior of glass fiber reinforced polymer matrix composite plates were investigated for different fiber orientations and lay-ups. The natural frequencies and damping factors of the composites were first evaluated experimentally by using the impulse technique. The natural frequencies were then evaluated theoretically by performing modal analysis. The results indicated good agreement between the experimental and theoretical values. The damping factors were also evaluated theoretically by using the specific damping capacity (SDC) model. Again, a good agreement between the experimental and theoretical values was evident. The results revealed that for a given fiber volume fraction the damping could be improved by reducing the strand diameter of fibers.