Typically, most of the aerospace and automotive components and mechanical structures are subjected to a cycling and/or fluctuating loads when in service. Hence, these structures are likely to fail due to fatigue if the applied cycling stress is at an adequate level to initiate and propagate the crack. However, aluminium and its alloys are ideally used in industrial application because of its weight to strength ratio. Furthermore, aluminium alloys provide high resistance to corrosion and excellent fatigue resistance. Nevertheless, in some applications where an alternative load is applied over an intense and persistent number of cycles, the use of an aluminium alloy will be on the margin due to its fatigue strength. Therefore, in order to improve its fatigue lifetime, the aluminium alloy will be treated either by Laser Shock Peening (LSP) or by Conventional Shot Peening (CSP), both of which are forms of mechanical surface treatment. This research will investigate the Laser Shock Peening (LSP) and Conventional Shot Peening (CSP) on the fatigue crack growth behaviour and the fatigue properties of the 2024-T4 aluminium alloy. This investigation focused on the role that the peening induced residual compressive stress, surface morphology and hardness on the crack growth rate and the fatigue life of the test specimens. Furthermore, a comparison of the induced residual compressive stress depth measurement between the two surface treatments (LSP and CSP) will be explored within this study. Finally, from this research a recommendation for when and where each of the two surface treatments (LSP and CSP) could be implemented and how they will be beneficial for the structural integrity of the parts and/or components which have experienced the penning.