ZrN/Si 3 N 4 multilayer coating that alternates with either nanocrystalline ZrN or amorphous Si 3 N 4 interlayers was fabricated by reactively magnetron sputtering in an Ar-N 2 mixture atmosphere. The thicknesses of the nanocrystalline ZrN and the amorphous Si 3 N 4 interlayers are~12.5 and 2.5 nm, respectively. The ZrN/Si 3 N 4 coating exhibits a promoted hardness of 28.6 ± 1.2 GPa when compared to the binary ZrN. Microstructure evolution just underneath the nanoindentation impression of the ZrN/Si 3 N 4 multilayer coating has been investigated. The result indicates that both ZrN nanograin rotations and plastic flow of the Si 3 N 4 interlayers contribute to the permanent deformation of the multilayer coating induced by the nanoindentation. In addition, the introduction of the a-Si 3 N 4 interlayers hinders both the initiation and propagation of microcracks when the multilayer coating was applied to the scratch test. The propagation deflection of the microcracks was observed attributed to the heterogenous interface, which produces the hardness promotion of the multilayer coating eventually.