A computational framework built on an effective-medium theory and mean-field homogenization is used to design particulate copper (Cu) composite for high-performance heat spreaders for electronic devices. Several potential particulate types as a second-phase are considered based on their intrinsic properties to design various Cu-composite heat-spreaders leading to desirable properties such as low coefficient of thermal expansion (CTE), low density, and improved structural response without compromising on required thermal conductivity. Based on computational predictions, the thermal interface of matrix particulate is found to be the dominant factor for maintaining required thermal conductivity (~300 W m-1 K-1), which suggested ceramic particles, particularly Beo, SiC, and AlN, as preferred candidates when loaded up to 30 vol%. Due to very high thermal conductivity and low CTE, diamond particles demonstrated the best results provided its wettability with copper is improved as a result of the surface coating. To validate the model results, numerous Cu composites with diamond as a second-phase are sintered using the spark plasma sintering technique, and the experimental data is found in close agreement with the predictions. The Cu composites containing Ni-coated diamond particles exhibited thermal conductivity more than the value of pure Cu at extremely low volume concentration (5%). The effect of particle size is also studied and it is found that the composites sintered with sub-micron particles resulted in more porosity as compared to micron-sized particles, which displayed direct bearing on thermal and mechanical properties as demonstrated by experimental data. The measured data on densification and particle–matrix interface condition is used in calibrating the models for establishing their effect on resulting thermal and structural properties. The presented integrated computational design methodology is validated using experimental data, which is expected to help the researchers and electronic industry develop high-performance heat spreaders with tailored properties.