In the present study, selective laser melting (SLM) was used to successfully fabricate Inconel 718–tungsten carbide (WC) composites. The processing parameter optimization results reveal that nearly non-porous composites (99.54%) were achieved with the laser power of 220 W, scanning speed of 850 mm s−1, and the hatch spacing of 150 μm. The microstructural characterization unveils that elongated grain structure in the heat flow direction was observed in the case of pure IN718 while WC particles served as obstacles to hinder the grain growth in the composites. The formation of in situ intermediate layer and the strong interfacial bonding between WC super-hard particles and the matrix acted as load bearing and significantly contribute to the overall properties of composites. Mechanical tests indicate significant improvements of microhardness and tensile strengths, although a drop in strength was observed when the amount of WC reached 15 wt.%. In addition, the thermal experiment shows that the composites are dimensionally stable at higher temperature compared to their monolithic counterpart. The findings suggest that the developed IN718-WC composites can be utilized in many critical engineering applications in nuclear sector.