This paper discusses the use of Plasma Pressure Compaction to consolidate hafnium diboride powders. The effect of carbon addition on densification was studied. The influence of consolidation temperature on microstructure, density, and hardness of the bulk sample is presented. The interrelationship between microstructure and properties of the bulk sample are rationalized in light of the intrinsic influence of carbon content and the extrinsic influence of consolidation temperature.