Aluminium alloy AA2219 reinforced with graphene/MWCNT nanocomposites having near theoretical densities has been successfully fabricated by high-energy ball milling followed by vacuum hot pressing. Effect of varying graphene and MWCNT content was studied on different aspects of processing of the composites. The particle size increases during milling due to cold welding; but the presence of reinforcement restricts and the resultant microstructures exhibited a layered morphology with graphene/MWCNT between particle boundaries. The composite with 0.5 wt.% reinforcement (graphene/MWCNT) content exhibited peak hardness, and further additions led to a decrease in hardness owing to the agglomeration of reinforcement at particle interfaces. The present study reveals that graphene is a better reinforcement compared to MWCNTs in aluminium matrix. This is attributed to the sheet-like morphology of graphene which covers the matrix powder particles more effectively compared to tube-like MWCNTs in providing more matrix–reinforcement contact points leading to better sintering. © 2017, Springer Science+Business Media, LLC and ASM International.