The effect of mechanical activation on the atmospheric pressure leaching of a lateritic nickel ore was investigated to develop a superior alternative. Under the influence of mechanical activation, certain physico-chemical changes were observed. Accelerated leaching kinetics and less sulfuric acid consumption were found as the most beneficial effects of mechanical activation. 80.6% Ni and 84.5% Co in leach were obtained with the mechanically activated sample after 2 h of leaching in 30% H2SO4 at 85 C-omicron and 1/2.5 solid/liquid ratio (w/w). When non-activated sample was leached under the same conditions, similar metal extractions could be obtained after 8 h of leaching. Finally, a process flow sheet was developed including mechanical activation of the laterite, agitation leaching, iron precipitation step, and nickel-cobalt solvent extraction. (C) 2017 Elsevier B.V. All rights reserved.