This work reports a new electrochemical monitoring platform for sensitive detection of Cu2+ coupling click chemistry with nanogold‐functionalized PAMAM dendrimer (AuNP‐PAMAM). The system involved an alkyne‐modified carbon electrode and an azide‐functionalized AuNP‐PAMAM. Initially, the added Cu2+ was reduced to Cu+ by the ascorbate, and then the azide‐modified AuNP‐PAMAM was covalently conjugated to the electrode via Cu+‐catalyzed azide‐alkyne click reaction. The carried AuNPs accompanying PAMAM dendrimer could be directly monitored by stripping voltammetry after acidic pretreatment. By introduction of high‐loading PAMAM dendrimer with gold nanoparticles, as low as 2.8 pM Cu2+ (ppt) could be detected, which was 125‐fold lower than that of gold nanoparticle‐based labeling strategy. The method exhibited high specificity toward target Cu2+ against other potentially interfering ions, and was applicable for monitoring Cu2+ in drinking water with satisfactory results.