Nanocomposite TiSiN coatings were successfully synthesized at a temperature and N-2 partial pressure of 350 degrees C and 0.02 Pa, respectively, from TiSi alloy targets with Si content of 20 at. % by using a large area filtered arc deposition technique. Scanning electron microscopy, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to investigate the surface morphology, crystalline structure, grain size, composition, and bonding structure of the deposited coatings. Nanoindentation was used to characterize the mechanical properties of the deposited coatings. It was found that adding Si into TiN coatings reduces the grain size significantly from 16.9 to 5.8 nm, changes the orientation from (111) to (220) preferred orientation, and increases the hardness and Young's modulus from 33 and 376 GPa to 51 and 449 GPa, respectively. XPS and XRD results show that the Si/Ti atomic ratio in the coatings is 0.17 and the deposited TiSiN coatings consist of nanosized TiN grains encapsulated by amorphous Si3N4 layer, corresponding to the superhigh hardness of the TiSiN coatings. The high plasma density, ion energy, and ion reactivity of the filtered cathodic arc plasma contribute to the formation of the nanocomposite TiSiN coatings at low temperature and low N-2 partial pressure.