Severe plastic deformation (SPD) processes were used in mixing and consolidating aluminum based nanocomposites containing various amounts of C nanoparticles. A planetary ball milling machine was used to mix the powders, and back pressure equal channel angular pressing (BP-ECAP) for consolidation. For comparison, Al-Al2O3 nanocomposites were processed by the same processing method. TEM observations showed that the combination of the two SPD processes was effective in dispersing the C nanoparticles in the Al matrix, and better dispersion was achieved by increasing the number of ECAP passes. Especially in Al-5 wt% C after ECAP consolidation for 24 passes, the compressive plastic strain was significantly improved. The Al-Al2O3 materials appeared to have better particle distribution and ductility compared to the Al-C materials although their strengths were lower.