Mechanical behavior of multi-walled carbon nanotubes (MWCNTs) reinforced aluminum matrix nanocomposites was evaluated microstructurally and mechanically using density measurement, Vickers hardness test and nanoindentation. Nanocomposites containing 1, 2 and 5 wt% of CNTs were synthesized with a combination of ball milling and powder metallurgy routes to investigate the effects of CNTs content and milling time on mechanical properties of the nanocomposites. Findings revealed that milling time plays an important role in the dispersion of MWCNTs within the Al matrix and subsequently in the mechanical properties of nanocomposites. Hardness and Young's modulus of the nanocomposites were improved significantly with increasing CNTs content and where a homogenous dispersion of CNTs was obtained. Bulk densities of composites were found to decrease with increasing CNTs content at a constant milling time but increased with increasing the milling time at a constant amount of CNTs. (C) 2015 Elsevier B.V. All rights reserved.