Filled high thermally conductive polymer composites will be vital materials to resolve heat dissipation problem in electronics. Herein, boron nitride nanosheet/silver nanoparticles (BNNSs/AgNPs) hybrids were prepared through liquid exfoliation and chemical reduction method, and then were added into epoxy resin (EP) to prepare BNNSs/AgNPs/EP composites. Previous study has proved that the thermal conductivities of the composites were enhanced with the addition of the BNNSs/AgNPs hybrids. Further, the over-all properties are also important to evaluate the performance of the polymer composites. In this paper, electrical and mechanical properties of the BNNSs/AgNPs/EP composites were investigated by thermogravimetric analysis, dynamic thermomechanical analysis and dielectric strength measurement. The result shows that the decomposed temperature is increased with the addition of BNNSs/AgNPs hybrids, the dielectric constant is increased with the increase of the filler content, and the dielectric constant of BNNSs/ AgNPs/EP is higher than that of BNNSs/EP. Energy storage modulus and glass transition temperature are both increased with increasing the filler content. Compared with BNNSs, impregnation of BNNSs/AgNPs hybrids to the EP makes the composite with higher glass transition temperature. The results indicate that the obtained BNNSs/AgNPs/EP composites, possessing good thermal, electrical and mechanical properties, will meet the requirement in modern electronics packaging field.