[en] Epitaxial thin films of double perovskite Nd₂NiMnO₆ (NNMO) have been fabricated on lattice matched SrTiO₃ substrate under different oxygen pressure (100 – 800 mTorr) by pulsed laser deposition technique. As the oxygen pressure increases of NNMO thin films, the out of plane lattice constant decreases which suggests that structural ordering enhances and defect concentration decreases with increasing oxygen background pressure. Two broad peaks around 516 cm^-1 and 657 cm^-1 are observed in the Raman spectra of the thin films, which are corresponds to the antisymmetric stretching and symmetric stretching modes, respectively. The films grown at low pressure exhibits the degradation in ferromagnetic behaviour of NNMO, which is caused by the existence of antisite disorders and mixed valence states of Ni³⁺ and Mn³⁺ in thin films due to oxygen vacancies or cation defects. The ferromagnetic properties such as saturation magnetization enhance of NNMO thin films with increasing oxygen pressure during growth, while the transition temperature remains unchanged. (author)