Abstract The oxygen deficient neodymium nickel perovskite, NdNiO 3− x , has been obtained by different low temperature-low oxygen pressure synthetic procedures. Besides a solid-matrix based route, both ordered and disordered chemical-precursors have been used as starting products. X-ray powder diffraction shows that the structure of this defective perovskite is orthorhombic. The study of the grain morphology of the products as resulting from the different synthetic procedures indicates that the main parameter determining the average particle size, which is in the nanometer range, is the maximum temperature achieved in the synthesis. Resistivity and DSC measurements show the existence of a metal to insulator transition at ca. 175 K. The anomalous behaviour of the resistivity in the insulator zone is discussed.