A coumarin Shiff-base derivative, salicylaldehyde-N-(6-phenylazo-coumarin-3-formyl)-hydrazone(1), was obtained by simple organic synthesis from cheap and commercially available starting materials. Sensor 1 exhibits a very weak fluorescence emission, however, in the presence of acetate ions “turn-on” fluorescence is observed, which results from binding-induced conformational restriction of the fluorophore. Importantly, sensor 1 can also be used as colorimetric chemosensor for the anions with strong basicity, which is easily observed from yellow to red by naked eyes. Consequently, compound 1 can behave as a colorimetric and fluorescence sensor for biologically important F-, CH3COO- and H2PO4- in the presence of the other anions tested such as Cl-, Br- and I- in dimethyl sulfoxide(DMSO). A coumarin Shiff-base derivative, salicylaldehyde-N- (6-phenylazo-coumarin-3-formyl) -hydrazone (1), was obtained by simple organic synthesis from cheap and commercially available starting materials. , however, in the presence of acetate ions “turn-on” fluorescence is observed, which results from binding-induced conformational restriction of the fluorophore. Importantly, sensor 1 can also be used as colorimetric chemosensor for the anions with strong basicity, which is easily observed from yellow to red by naked eyes. Therefore, compound 1 can behave as a colorimetric and fluorescence sensor for biologically important F-, CH3COO- and H2PO4- in the presence of the other anions tested such as Cl-, Br- and I-in dimethyl sulfoxide (DMSO).