SiO2-Al2O3 support material was prepared by sol-gel method, followed by calcination at 500, 1000 and 1500 degrees C. The supported nickel catalyst containing 5 wt% was obtained by impregnating a known mass of the calcined support material with nickel sulfate solution followed by drying and reduction with hydrazine hydrate at 80-100 degrees C. The prepared catalysts were fully characterized by XRD and SEM, EDX and ESR. The hydrogenation of p-nitrophenol into p-aminophenol was performed using hydrazine hydrate as hydrogen donor. The product of the reaction was examined using IR, and NMR. The results showed that the degree of crystallinity of the support affects the catalytic activity of nano-sized Ni catalyst. It was observed that as the degree of crystallinity of the support material increases the catalytic activity increases. On the other hand, intermolecular interaction between nano-nickel clusters disappears completely in samples whose support was calcined at 1500 degrees C. Crown Copyright (C) 2008 Published by Elsevier B. V. All rights reserved.