A series of TiB2-TiNiFeCrCoAl high-entropy alloy (HEA) composites with HEA contents of 5, 10, and 20 wt.% were fabricated to a relative density of above 95% without applied external pressure at 1550 degrees C in flowing argon. Research indicates (i) the formation of liquid HEA is promoted with the assistance of an optimized ball mill process, which facilitates the sintering through a liquid phase sintering mechanism, and (ii) HEA can react with the oxide impurities in TiB2 and can consequently enhance the densification. Continual observations on microstructures and properties indicate that the sintered composites have a submicronmeter grain size of 0.90 +/- 0.11, 0.79 +/- 0.09, and 0.74 +/- 0.07 m; a high hardness of 23.3 +/- 0.9, 21.6 +/- 1.0, and 17.5 +/- 1.2 GPa; and a high indentation fracture toughness of 8.7 +/- 0.4, 11.1 +/- 0.6, and 12.8 +/- 0.6 MPam(1/2), respectively, for samples with 5, 10, and 20 wt.% HEA. The addition of HEA to TiB2 can significantly enhance the densification, results in fine microstructures, and improve the mechanical performance.