The application of carbon nanotubes (CNTs) as reinforcements in aluminum (Al) matrix composites was studied enormously with different fabrication methods due to the outstanding properties of CNTs. As known, precipitation hardening is important in the mechanical property enhancement of suitable Al alloys, as well. Especially, T6 heat treatment is one of the most aforementioned treatments where solution heat treatment and artificial aging are applied, re-spectively. In this study, CNT-reinforced 6063 Al alloy matrix composites were fabricated by vacuum-assisted infiltration into a preform method, and T6 heat treatment of composites was realized. The aging behavior of samples was introduced by derivation of mechanical proper-ties and results were discussed in view of microstructural characterization. It was found that decent matrix reinforcement interfacial bonding and aging capability improved by the pres-
ence of MgAl2O4 and Al4C3 were successfully provided through the fabrication method. After aging, composites reached a hardness of 123.6 HV where the hardness value of 59 – 65 HV can be achieved by aging of 6063 Al alloy and 79 HV by the CNT reinforcement only. Moreover, the peak tensile strength value of 254 MPa reached by the aging of CNT/6063 Al composites is 38% higher than aged 6063 Al alloy and 113% higher than solely CNT-reinforced composites. In addition, the increase in the compressive properties in composites is also remarkable. Consequently, recent findings and discussions presented in the study provided an important understanding the effects of CNT existence on the aging behavior of Al alloys.