We first synthesized ultra-fine TiB2 and TiC powders using a modified carbothermal reduction approach. We further fabricated a series of TiB2-TiC cermet using various binder materials including Co, Ni, and high-entropy alloys. Due to the fine particle size of the synthesized powders, the samples can be sintered to a very high relative density (as high as >99%) with different compositions of the binder phase (from 3 to 20 wt%). We further found that high-entropy alloys can refine the grain size in cermet than Co and Ni binder phases. We hypothesized that the high-entropy alloy binder could alter the diffusion rate, the solubility, and the solid-liquid surface energy. With the fine grain size, mechanical properties including hardness and fracture toughness, have been improved. We further observe the ceramic-binder interface to study the hardening and toughening mechanisms.