Y In this study, diamond/aluminum composites were fabricated by the use of gas pressure infiltration. The effects of SiC-coated diamond particles on composite performance were investigated in terms of: (1) controlling the thermal conductivity (TC) during composite fabrication and (2) providing long-term stability. Al4C3 spontaneously forms at the interface of the diamond particles and the Al matrix. An excess amount of Al4C3 interphase adversely affects the composite, due to its low TC and hygroscopic behavior. Because the SiC coating of diamond particles suppressed the formation of Al4C3 during the fabrication, the composite contained a low amount of Al4C3 and showed higher a TC (528 W/m.K) than uncoated diamond/Al composite (376 W/m.K), along with significantly higher moisture resistance. The thermal expansion coefficient (CTE) of the SiC-coated diamond/Al composite was determined to be 7.2 ppm/K at room temperature. The composite exhibited long-term stability up to 500 degrees C as the Al-C reaction was prevented by the SiC coating. Moreover, it displayed excellent thermal shock resistance between 300 degrees C and room temperature.