Fully densified diamond-reinforced aluminum (denoted as Al-D) matrix bulk materials were successfully fabricated using a low-pressure cold-spray process. Two different temperatures of the processing gas were used in order to deposit the Al-D composite powders, and the thermophysical properties of the Al-D bulk materials were investigated. The interfaces between the matrix and reinforcement were observed by scanning electron microscopy in order to understanding of the relationship between the thermophysical properties and microstructure. The thermophysical properties of the Al-D bulk materials were better than those of pure Al processed under the same conditions. We believe that this cold-spray process can be successfully applied for fabricating Al-D bulk materials.