NiO thin films grown on Si(100) substrate and annealed at 500°C were irradiated with 120 and 200 MeV Au ions. The effect of Au ion energy on lattice parameter and hence the stress profile of NiO films were studied. Though the lattice parameter of NiO decreases with increasing ion fluence for both the ion energy cases the sanme decreases slightly larger amount at higher fluences for the NiO film irradiated with 200 MeV Au ions. Stress calculated form the lattice parameter indicated the development of compressive stress in both the ion energies. Our study indicated that the higher value of stressed region for 200 MeV Au ion irradiation case and the same may be due to higher electronic energy loss of the ion in the NiO medium.