In this paper spent nickel catalyst (Ni/diatomite) resulting from hydrogenation process of edible oil was regenerated. To reach this aim heat treatments with hydrogen flushing was employed. The impact of particle size, reaction time and temperature on spent nickel catalyst regeneration were studied. The structural characteristics, elemental and chemical analysis of the samples were studied by Fourier transform infrared spectroscopy and X-ray fluorescence. The regenerated catalyst and fresh catalyst were tested in an experimental hydrogenation process. Noticeable regeneration achieved as under; mesh number: 200, time: 1 h and temperature: 450 degrees C. All Results showed that spent nickel catalyst could be regenerated directly. Through this method no part of the spent nickel catalyst was left in the environment and no reagent was used. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.