We have synthesized multi-wall carbon nanotube (MWCNT)-reinforced Al matrix composites. The Al/MWCNT composite powders were prepared by ball milling using pristine Al or ball-milled Al powders as starting materials. The composite powders were consolidated by a conventional cold-compaction, followed by sintering. Uniform dispersion of individual MWCNTs within the matrix was in particular a critical factor for obtaining high density and high quality Al/MWCNT composites. Compared to pristine Al powders as starting materials, the Al powders previously attrition-ball-milled with carbon-based PCA (process control agent) in an ammonia atmosphere resulted in a better distribution of carbon nanotubes within the Al matrix and a higher density after sintering.