Developing excited-state intramolecular proton transfer (ESIPT) emitters with high photoluminescence quantum yields (Phi(PL)s) and long fluorescence lifetimes in solid state remains a formidable challenge. In this study, we integrated the molecular design tactics of thermally activated delayed fluorescence (TADF) into ESIPT molecules with the goals of improving their Phi(PL)s and increasing their fluorescence lifetimes. Two proof-of-concept molecules, PXZPDO and DMACP-DO, were developed by adopting symmetric D-pi-A-pi-D molecular architectures (where D and A represent donors and acceptors, respectively) featuring electron donating phenoxazine or a 9,9-dimethyl-9,10-dihydroacridine moiety, an ESIPT core beta-diketone, and phenylene pi-bridges. Both molecules exhibited sole enol-type forms stabilized by intramolecular hydrogen bonds and exhibited a unique and dynamic ESIPT character that was verified by transient absorption analyses. Endowed with distinct TADF features, PXZPDO and DMACPDO showed high Phi(PL)s of 68% and 86% in the film state, coupled with notable delayed fluorescence lifetimes of 1.33 and 1.94 mu s, respectively. Employing these ESIPT emitters successfully achieved maximum external quantum efficiencies (n(ext)s) of 18.8% and 23.9% for yellow and green organic light-emitting diodes (OLEDs), respectively, which represent the state-of-the-art device performances for ESIPT emitters. This study not only opens a new avenue for designing efficient ESIPT emitters with high Phi(PL)s and long fluorescence lifetimes in solid state but also unlocks the huge potential of ESIPT emitters in realizing high-efficiency OLEDs.