ZrB 2 /Zr 2 Al 4 C 5 composite ceramics with different volume contents of Zr 2 Al 4 C 5 formed in situ were fabricated by the spark plasma sintering technique at 1800 ° C. The content of Zr 2 Al 4 C 5 was found to have an evident effect on the preparation, phase constitution, microstructure as well as the mechanical properties of ZrB 2 /Zr 2 Al 4 C 5 ceramics. The results indicated that sinterability of the composites was remarkably improved by the addition of Zr 2 Al 4 C 5 compared to the single-phase ZrB 2 ceramic. The microstructure of the resulting composites was fine and homogeneous, the average grain size of the ZrB 2 decreased, and the average aspect ratio of the Zr 2 Al 4 C 5 increased with the increase in the amount of Zr 2 Al 4 C 5 . As the content of Zr 2 Al 4 C 5 increased, both the Vickers hardness and Young's modulus of the composites first increased and then decreased. The fracture toughness of the ZrB 2 –40vol% Zr 2 Al 4 C 5 composite was 4.25MPam 1/2 , which increased by approximately 70% compared to the monolithic ZrB 2 ceramic. The improvement was mainly attributed to the toughening mechanisms such as the layered structure toughening, crack deflection and crack bridging, caused by the in situ formed layered Zr 2 Al 4 C 5 inclusions.