TiN layers deposited by Closed Field Unbalanced Magnetron Sputtering (CFUBMS) on M2 tool steel were heat treated in an inert argon atmosphere at 700, 800 and 900 °C for 3 h. The coatings were analyzed by microhardness, XRD and scanning electron microscopy (SEM)–energy dispersive spectrometry (EDS). It was found that heat treatment at 700, 800 and 900 °C changed the mechanical properties, microstructure and composition of film. The golden yellow color of TiN films changed after heat treatment. The high values of the microhardness observed for as-deposited films decreased after heat treatment. The peak intensities of TiN decreased and the intensities of α-Fe increased with an increase of heat treatment temperature. The variation in chemical composition of films was determined as a function of the heat treatment. Microcracking of the surface morphology of films heat treated at 900 °C was observed.