Bulk Mg–3%Al alloy-based nanocomposites containing graphene nano-platelets (GNPs) were synthesised using the powder metallurgy technique incorporating energy efficient hybrid microwave sintering and hot extrusion. GNPs in amounts of 0.1, 0.3 and 0.5 wt-% were investigated as reinforcements. Microstructural characterisation accomplished using optical, scanning and transmission electron microscopy revealed the presence of minimal porosity (<1%), a uniform distribution of GNPs in the matrix and a reduced grain size as a result of the presence of GNPs. The results of mechanical property characterisation revealed an overall improvement in micro-hardness and compressive response, due to the presence of GNPs, with best results exhibited by the Mg–3Al/0.3% GNPs composite. The ductility under compressive loading for composite samples remained higher than 20%.