A new turn-on fluorescent chemosensor, DPPL₁, was rationally designed and synthesized based on diketopyrrolopyrrole (DPP), which presented high sensitivity and selectivity for Zn²⁺. Specifically, DPPL₁ presented a large emission enhancement and a 70 nm blue-shift upon Zn²⁺ binding. ¹H NMR titrations, studies into the pH effects and DFT calculations further proved that this phenomenon was due to both photo-induced electron transfer (PET) and intra-molecular charge transfer (ICT) processes. More importantly, DPPL₁ was successfully used for imaging Zn²⁺ in living HeLa cells. To the best of our knowledge, this is the first DPP-based fluorescent chemosensor to recognize Zn²⁺ ions in living cells with a large blue-shift and a fluorescent enhancement based on both photo-induced electron-transfer (PET) and intramolecular charge-transfer (ICT) effects. Meanwhile, we have also provided a new effective platform for the development of fluorescent chemosensors for other analytes.