Water-dispersible core/shell/shell ZnSeS/Cu:ZnS/ZnS quantum dots (QDs) capped with 3-mercaptopropionic acid (3-MPA) were successfully prepared via a one-pot method. The dots are photostable, exhibit a Cu-related photoluminescence (PL) emission located at 500 nm and a PL quantum yield of 21%. The PL of ZnSeS/Cu:ZnS/ZnS QDs was demonstrated to be selectively quenched by Pb2+ ions and a method for the rapid and sensitive detection of Pb2+ in real water samples was developed. Under the optimized conditions, the PL intensity of ZnSeS/Cu:ZnS/ZnS QDs is almost linearly dependent on the Pb2+ concentration in the range of 0.04 to 6 μM and the detection limit is 21 nM in water. Based on PL lifetime and UV-visible absorption measurements, a dynamic quenching mechanism was demonstrated. ZnSeS/Cu:ZnS/ZnS QDs were also demonstrated to be efficient probes for the detection of Pb2+ in real water samples. The developed method is rapid, simple and sensitive and demonstrates that ZnSeS/Cu:ZnS/ZnS QDs can be used as non-toxic probes to sense Pb2+ ions in aqueous solution.