Use of aluminium alloy in aerospace and automotive industry has increased due to their high strength to weight ratio. Oil jet peening, a surface modification process is developed to impart compressive residual stresses on the surface of the metallic materials and resulted in significant surface hardening with associated grain refinement. Unlubricated fretting tests were performed on the oil jet peened and unpeened aluminium samples using ball-on-flat configuration at constant slip amplitude and at different applied normal loads. At low applied normal loads, the contact region between the mating surfaces makes the asperities interlock each other resulting in high tangential force coefficient. Due to micro-displacement between the interfaces of two mating members, cracks initiate and cause debris formation. The steady state tangential force coefficient, wear volume and specific wear rate of the oil jet peened samples were lower than those of the unpeened (as-received) samples for all the conditions tested and this is mainly attributed to increased substrate strength. A complex adhesion and oxidation type of wear mechanism was observed at low applied normal loads and at high applied normal loads abrasion was found to be a dominant wear mechanism. © 2012 Elsevier B.V.