Silicon nitride containing various com positions of as-received TiC a nd TiN-coated TiC, were hot pressed at 1800 degrees C for 1 h in a nitrogen atmosphere. In TiN-coated TiC/Si3N4 composites, TIC reacted first with the TiN coating to form a titanium carbonitride interlayer at 1450 degrees C, which essentially reduced further reactions between TiC and Si3N4 and enhanced densification. TiN-coated TiC/Si3N4 composites exhibited better densification, hardness, flexural strength a nd fracture toughness than those of as-received TiC/Si3N4. The toughening mechanisms for as-received TiC/Si3N4 and TiN-coated TiC/Si3N4 composite were attributed to crack deflection, load transfer and crack impedence by the compressive thermal residual stress.