The effect of Si addition on the microstructure and mechanical property of TiN film was investigated. The Ti-Si-N films were deposited on high-speed steel substrate by a plasma-assisted chemical vapor deposition (PACVD) technique using a gaseous mixture of TiCl4, SiCl4, N-2, Ar, and H-2. The Si content in the film was increased up to 15 at.% by increasing the mixing gas ratio of SiCl4 to TiCl4. The Si was found to be codeposited in the form of Si3N4/TiN composite. The Si addition to TiN film caused the microstructural changes such as grain size refinement, randomly oriented microstructure, and nano-sized precipitates of silicon nitride in the TiN matrix. The Ti-Si-N film containing a Si content of similar to 7 at.% showed the micro-hardness value of similar to 3400 HK, which was largely an increased value in comparison with compared with similar to 1500 HK of the pure PACVD-TiN film.