Heat treatment of ultra-fine WC-13Co powders was carried out prior to cold compaction, in an attempt to improve the sintered density. The findings indicate that a preheat treatment of ultra-fine or nano-sized powders significantly improves the densification process. This study showed that a low compacting pressure, < 200 MPa, can be effectively used through this technique to retain ultra-fine structure. The densification behavior of preheated powder was compared with the samples prepared by a conventional technique and explained with size distribution, standard deviation, and surface effect.