We have synthesized a new indole functionalized rhodamine derivative L1 which specifically binds to Cu2+ in the presence of large excess of other competing ions with visually observable changes in their electronic and fluorescence spectral behavior. These spectral changes are significant enough in the NIR and visible region of the spectrum and thus enable naked eye detection. The receptor, L1, could be employed as a resonance energy transfer (RET) based sensor for detection of Cu2+ based on the process involving the donor indole and the acceptor Cu2+ bound xanthene fragment. Studies reveal that L1–Cu complex is selectively and fully reversible in presence of sulfide anions. Further, fluorescence microscopic studies confirmed that the reagent L1 could also be used as an imaging probe for detection of uptake of these ions in HeLa cells.