This work presents the deposition of Ni nanoparticles on a potassium hydroxide (KOH) activated carbon (AC) support by an electroless deposition (ED) technique without using sensitization and activation surface pretreatments. The hydrogen storage properties of Ni-activated carbon nanocomposites (Ni/AC) were investigated at room temperature and under moderate pressure. The chemical composition, morphology and textural parameters are characterized using an inductively coupled plasma spectrometer (ICP), scanning and transmission electron microscopy (SEM and TEM) and N-2 adsorption isotherms. Fine and well-dispersed Ni nanoparticles were obtained by ED that had spherical shape with an average size of 5 nm. The hydrogen storage capacity of the AC can be improved through Ni loading; which results in a hydrogen storage enhancement factor of two compared with the Ni-free AC. This enhancement factor is due to the greater interactions between the Ni and the AC, which facilitate the hydrogen spillover mechanism. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.