A new physical scheme is presented for the detection of copper, based on the use of a fluorescently labeled dendrimer anchored on a gold nanowire. Upon light illumination surface plasmon resonance was generated from the gold nanowire, which promoted quenching of the dendrimer fluorescence as a result of the energy transfer between the dendrimer and the copper ions. The monotonic dependence of the fluorescence quenching on copper concentration was exploited to reach a copper detection sensitivity of 2 nM. In addition, the fluorescence of the labeled dendrimers was quenched specifically by copper in a matrix of common metal ions. Using simulations we calculated the enhanced optical near field for a dendrimer-coated gold nanowire illuminated by a TM-polarized plane wave, which provided a physical basis for the sensitive copper detection using the current experimental scheme.