Metal Diamond Composites exhibit promising properties for thermal management applications. A tailored design of the interface between the material partners is essential to exploit the potential of the reinforcement. In this study a cost efficient and easy to apply coating technique based on thermal diffusion was investigated and thin nanometer to micrometer coatings of various metals were successfully applied onto diamond powders. Besides the study of the diffusion process itself, the resulting layer thicknesses and interlayer compositions, the coated diamonds were introduced in a metal matrix by hot pressing and the thermal properties of the composite were measured. Thermal conductivities above 600W/mK and a coefficient of thermal expansion of 8-10ppm/K were achieved in such composites. In addition, thermo-mechanical stability was tested by thermal cycling under harsh conditions. Various sample geometries were produced to show the benefits of PM processing which enables combining excellent thermal properties with good surface finish and complex shaping.