This research studies the effect of friction stir processing (FSP) on the mechanical properties of LM-25 aluminium alloy. The research is conducted by trying different processing parameters (spindle speed and feed rate) settings to observe the effect of such parameters on the alloy. A tensile test and a Vickers hardness test are carried out to analyse the result of the FSP on the mechanical properties of the alloy. The results show a notable improvement in the mechanical properties and show a relation between the processing parameters and the mechanical properties of the alloy. Improvement in strength, toughness, and hardness of the alloy is linked directly to the parameters of the friction stir processing of the alloy.