Aluminum-diamond composites were produced using selective laser melting (SLM) from mechanically mixed diamond and Al12Si powders for use in thermal management applications. The feasibility of SLM for both interface tailoring and simultaneously densification, which are the key for determining the overall thermal conductivity (TC) of the composites, has been investigated. The results indicate that the interface structure of the as-built composites can be controlled, despite the complex physical and chemical nature of SLM. A ‘clean’ diffusion-bonded interface revealed at the micron scale, which is desirable for enhancing TC, was obtained at a laser energy density of 95.2 J/mm 3 . This demonstrates a possible new potential of SLM in creating metal matrix composites for functional applications. However, despite manipulation of the processing parameters, it was not possible to achieve a relative density above 90%. Thus, how to realize near full density, while maintaining such a ‘clean’ interface during SLM remains a key technical problem for the future. The complex metallurgical mechanisms responsible for interface evolution and microstructure formation are discussed in detail with the aid of finite element analysis, and further densification strategies are proposed.