The boride ceramics have been attracting considerable attention as one of the newest advanced ceramics. In particular, titanium diboride (TiB2) has various desirable properties, such as a high melting point (3253 K), high hardness (32 GPa), and moderate electrical conductivity (105S). One of its major disadvantages, however, is poor sinterability. In this study, the effect of sintering aids addition on the pressureless sintering process of TiB2 ceramics was investigated. The addition of both Cr and C or Cr3C2 as the sintering aids accelerated the densification of TiB2 significantly. Simultaneous addition of about 5 to 10 mass% Cr and C or Cr3C2 resulted in high density, high bending strength and high Vickers hardness. According to the X-ray diffraction data of TiB2 composites fired at 1173 to 2173 K showed that Cr and C or Cr3C2 reacted with TiB2 to form CrB and TiC during the sintering process. CrB and TiC were formed at the grain boundaries of TiB2. Also, the solid solution between TiB2 and sintering aids was recognized. The SEM micrograph observation supported that a liquid phase was significantly concerned in the sintering of TiB2. The fracture surface of TiB2 sintered body showed both transgranular and intergranular fracture mode. It is considered that the addition of both Cr and C or Cr3C2 was effective in promoting the bonding between grains and removing pores to achieve high density in the sintered body. Thus, a sintered body of TiB2 having increased density, high strength and high hardness can be obtained by the addition of Cr and C or Cr3C2 to TiB2.