Water contamination caused by heavy metal pollutants from industrial activities remains a pressing environmental concern. This study reports the development of a novel carbon paste electrode (CPE) modified with ethylenediaminetetraacetic acid (EDTA), polyvinyl alcohol (PVA), and multi-walled carbon nanotubes (MWCNTs) using a mechanochemical method for the electrochemical detection of Cu(II) ions. The modified electrode was thoroughly characterized to evaluate its functional groups, morphology, crystallinity, elemental composition, and electrochemical properties. Electrochemical measurements were performed using cyclic voltammetry (CV) and square-wave anodic stripping voltammetry (SWASV) under optimized conditions in 0.1 M NH₄Cl at pH 5. The EDTA/PVA/MWCNT-CPE exhibited a low detection limit (0.0457 μM), a wide linear range (0.1–2.7 μM), and excellent reproducibility (RSD = 0.51%), repeatability (RSD = 0.43%), and stability (95% retention after six days). Selectivity tests demonstrated high recovery for Cu(II) (99.7%) and Hg(II) (99.89%) with minimal interference. This simple, cost-effective sensor offers high sensitivity and selectivity, making it a promising candidate for Cu(II) detection in environmental monitoring applications.