For improving the mechanical properties of tungsten, HfC-W composites were fabricated by ball milling and spark plasma sintering process. The microstructure and mechanical properties of the composites were investigated. The interdiffusion of the Hf and W atoms during sintering produced a mixed carbide, identified as (Hf,W)C. This interfacial mixed carbide helped in developing a good interface joint with the adjacent W matrix. The increase in mechanical properties of the HfC-W composite at room temperature as well as high temperature was attributed to the reinforcement effect of the HfC particles. One of the strengthening mechanisms of the composite can be attributed to the formation of mixed carbide (Hf,W)C by interdiffusion at the interface, which assured the effective load transfer from the W matrix to the hard HfC particles.