Thermal stability and mechanical properties of zirconium tungsten nitride (Zr–W–N) thin films have been studied. Nano-structured Zr–W–N thin films have been deposited on Si (100) substrates by reactive magnetron sputtering at varying substrate temperatures T s (100°–600°C). For 100°C≤T s ≤600°C, X-ray diffraction patterns of the films show a crystalline fcc phase with (111) and (200) preferred crystallographic orientations of grains. Maximum wear resistance (H/E r ~0.22) and maximum resistance to fatigue fracture (H 3 /E r 2 ~1.0GPa) have been obtained for the film deposited at T s =400°C. Post annealing of the films deposited at 400°C has been carried out in air from 100°–600°C. Oxygen starts to be incorporated at 300°C and films begin to peel off above 400°C due to increase in oxygen incorporation. Hardness and elastic modulus of annealed films increase with increasing strain.