In order to decrease chemical consumption and improve surface quality in copper chemical mechanical polishing (CMP), functionalized multi-walled carbon nanotubes (MWCNTs) were innovatively employed in this study as lubricants and worked in synergy with 1,2,4-triazole (TAZ). The optimal TAZ concentration of 0.004 wt% was determined by dynamic polishing experiments, at which the surface roughness (Sq) could reach 2.15 nm. X-ray photoelectron spectroscopy analysis confirmed that TAZ can form a dense passivation film on copper surfaces, significantly inhibiting excessive corrosion. However, atomic force microscope measurements revealed that scratches appeared on the surface after polishing. To address this, three functionalized MWCNTs (MWCNTs-COOH, MWCNTs-OH, MWCNTs-NH 2) were further introduced from a mechanical perspective. Experimental results indicate that they can effectively improve surface quality through a synergistic mechanism of “rolling lubrication-pressure buffering,” with MWCNTs-OH exhibiting the best performance, further reducing surface roughness to 1.21 nm. The findings uncover the underlying mechanisms of nanomaterials' novel functions in CMP.