This study involves the investigation of mechanical damping and thermal stability of hybrid epoxy composites with two types of fillers, graphitized carbon nanofiber (CNF) and micron size silicon dioxide (SiO2) particles. While viscoelastic properties of the composites were characterized for the study of mechanical damping, the linear coefficient of thermal expansion (CTE) was evaluated for investigation of thermal stability of the hybrid composites. The effect of filler loading was investigated with respect to both mechanical and thermal stability of the hybrid composite materials. It has been found that the addition of 3% weight fraction of SiO2 particles along with 3% weight fraction of CNF can improve damping loss factors by up to 15.6% at room temperature while at the same time improving thermal stability with up to 15% reductions in CTE. This study also presents semi-empirical models which can account for both the fillers in prediction of viscoelastic properties and CTE of the hybrid composites. It is observed that there is reasonable agreement in both mechanical damping and CTE for the hybrid composites between the experimental data and the predicted data.