The aim of the study was to develop a simple and cost-effective method to improve thermal insulation and hydrophobicity of wood. Herein, we attempted to use commercially available silica aerogel powders suspended in ethanol to treat the wood by a simple vacuum impregnation process. The effects of particle size (20 µm and 40 nm) of silica aerogels and the number of impregnation cycles (1, 3, and 5 cycles) were examined on the thermal conductivity and the surface hydrophobicity. The results showed that the thermal conductivity of silica aerogel-impregnated wood decreased by approximately 38%. The water contact angle of the impregnated wood increased up to the maximum values 153° with a comparison with 80° of the untreated wood, indicating effective hydrophobization after silica aerogel impregnation. The tensile properties of the impregnated wood were found slightly improved. The results indicate that the impregnation of silica aerogel powders in wood can be a facile and efficient approach to prepare wood with thermal insulation and hydrophobicity, which may hold great promise to be employed in manufacturing wood-based materials used in interior decoration and buildings.