The development of a novel TiN‐reinforced silicon nitride/silicon oxynitride composite using an innovativein situTiN‐forming technique was investigated. Silicon powder compacts containing various amounts of TiO2(anatase structure) and sintering additives were nitrided under N2atmosphere and then further densified by hot pressing. The microstructure of the resultant composite was analyzed by X‐ray diffraction, scanning electron microscopy, and solid‐state nuclear magnetic resonance spectroscopy. The results of this study show that TiO2can be successfully converted to TiN during the nitridation of Si + TiO2mixture. The TiO2content affects not only the microstructure of the matrix but also the composition of the intergranular phase. The type and amount of sintering additives also show a significant effect on the microstructural development of the co