We report a stochastic nanopore sensing method for the detection of Cu²⁺ ions. By employing a polyhistidine molecule as a chelating agent, and based on the different signatures of the events produced by the translocation of the chelating agent through an α-hemolysin pore in the absence and presence of target analytes, trace amounts of copper ions could be detected with a detection limit of 40 nM. Importantly, although Co²⁺, Ni²⁺, and Zn²⁺ also interacts with the polyhistidine molecule, since the event residence times and/or blockage amplitudes for these metal chelates are significantly different from those of copper chelates, these metal ions do not interfere with Cu²⁺ detection. This chelating reaction approach should find useful application in the development of nanopore sensors for other metal ions.