FeN and FeTiN alloy films have been prepared by reactive sputtering. The structure and magnetic properties of the FeTiN and FeN films have been studied as a function of the N 2 flow rate R(N 2 ) and annealing temperature T A by X-ray diffraction (XRD) and a vibrating sample magnetometer. The as-prepared and annealed FeN films consist of the α-Fe and Fe 4 N phases but the FeTiN films are composed of the α-Fe and Ti 2 N phases. The coercivity, Hc, of the FeN films changes drastically with R(N 2 ) and T A , while that of the FeTiN films does not change with T A up to 500°C. These results indicate that the addition of Ti suppresses the formation of iron nitride phases and improves the thermal stability of FeN films.