ZrB2-ZrC-SiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1750 degrees C for 300 s under a pressure of 40MPa. Densification, microstructural, mechanical properties and oxidation behavior of the composites were investigated. Fully dense ZrB2-ZrC-SiC composites with a relative density of more than 99% were obtained at 1750 degrees C for 300 s. Vickers hardness of ZrB2-ZrC-SiC composites decreased with increasing ZrC content from 20 to 40 vol %, and composite containing 60 vol % ZrB2, 20 vol % ZrC and SiC sintered at 1750 degrees C for 300 s had the highest value of 21.1 GPa. The crack mode for the same composite was zigzag, and resulted in remarkable crack deflections and the highest fracture toughness value of 5.5 MPa.m(1/2). Oxidation of composites resulted in formation of protective layered oxide structures consisted of ZrO2 and Si-O rich layer in the form of SiO2 or SiO, and normalized mass change results increased with increasing oxidation temperature. (C) 2012 The Ceramic Society of Japan. All rights reserved.