An Excited State Intramolecular Proton Transfer (ESIPT) based water-soluble fluorescent chemodosimeter for the ratiometric detection of palladium ions has been rationally designed and developed. Based on the specific reactivity of palladium-promoted hydrolysis, the probe exhibited high selectivity and sensitivity towards palladium ions. Furthermore, the probe was successfully used for fluorescence imaging of Pd²⁺ in living cells.