A glassy carbon (GC) electrode was modified with poly(1,8-diaminonaphthalene) (p-1,8-DAN) that was coated with silver nanoparticles (Ag NPs) (size: 10.0-60.0 nm by TEM) by electrodeposition process using cyclic voltammetry (CV) technique. The resulting nanocomposite was characterized by FE-SEM, AFM, EDX, XPS, TEM and XRD. The surface area and the electrochemical characteristics of the electrode were investigated by CV and square wave voltammetry (SWV) techniques, and the probe preparation conditions were optimized. The electrode was used for individual and simultaneous determination of the heavy metal ions cadmium(II) (Cd), lead(II) (Pb) and copper(II) (Cu) in water samples by square wave anodic stripping voltammetry (ASV) using scan rate 0.005 V. s. The probe showed well separated anodic stripping peaks for Cd, Pb, and Cu. Attractive features of the method include (a) peak voltages of -1.02, -0.78 and - 0.32 V (vs. Ag/AgCl) for the three ions, and (b) low limits of detection (19, 30 and 6 ng.L, respectively. The electrode can also detect zinc(II) (Zn) and mercury(II) (Hg), typically at -1.36 V and + 0.9, respectively. Graphical abstract Schematic presentation of simultaneous electrochemical determination of Pb, Cd, and Cu at a poly(1,8-diaminonaphthalene)-modified glassy carbon electrode coated with silver nanoparticles.