Accumulative roll-bonding was adapted to fabricate a carbon nanotube (CNT)-reinforced aluminum matrix composite. Its microstructure was investigated by transmission electron microscopy, and it was confirmed that the nanotubes were embedded into the metal matrix while maintaining their multiwalled structure. Measurements revealed that the as-received CNTs had a bimodal diameter size distribution, while only nanotubes with diameters >30 nm and >30 walls were retained during four consecutive rolling operations at 50% reduction.