including cell metabolism, signal transduction, cell growth, apoptosis, and endocytosis. The development of simple and robust proton-recognizing fluorescent probes has been a research field of high interest. In this work, we describe the design and synthesis of a 2-quinolone Schiff base as a novel acidic fluorescent probe. The design strategy of the probe is based on non-classical hydrogen bonding in the form of an intramolecular three-centered hydrogen bond (THB). pH titrations at pH levels 2 and 7 indicate that there is enhancement of fluorescence with increasing proton concentration. Additionally, no interference of metal ions like Cu2+, Fe3+, Hg2+, Zn2+, Co2+, Cd2+, and Pb2+ ions were detected during these titrations.