Boron-doped diamond electrode surfaces were modified by a polyphenol-polyvinyl chloride membrane. The polyphenols were extracted from the skin of acorns, the fruit of the oak tree. The polymer film was applied on the boron-doped diamond electrode surface by solvent evaporation. The resulting polyphenol-polyvinyl chloride- boron-doped diamond electrode was used as a sensor for cadmium, lead, and nickel. The synergy between the chemically modified surfaces and the electrochemical performances of the boron-doped diamond microcell electrode were examined by differential pulse anodic stripping voltammetry at nanomolar concentrations of the three metal ions. The modified electrode provided a stable, sensitive, and selective response to cadmium, lead(II), and nickel(II) ions. The resulting detection limits were 0.0221, 0.25, and 0.00424 nmole L−1, respectively.