A rationally designed poly-(phenylenebutadiynylene) bearing urea functionalities (poly-1) was demonstrated to be a novel fluorescence turn-on probe for various anions. Poly-1 itself exhibits an extremely weak emission that was undetectable by the naked eye, whereas the fluorescence emission of poly-1 was significantly enhanced by the addition of anions. Based on the NMR, dynamic light scattering, and fluorescence decay measurements, the observed fluorescence turn-on response was determined to be realized by the fluorescence recovery based on the disassembly of the poly-1 aggregates, which was originally triggered by the anion recognition event at the urea units of poly-1.