© 2021 Elsevier B.V.Novel colorimetric and fluorimetric fluorescent coumarin-thizole based chemosensors 4a-b were synthesized and characterized using spectroscopic methods. The photophysical properties of the sensors were determined in six solvents by UV–Vis and fluorosence spectrometers. The sensitivity and selectivity of 4a-b towards anions were investigated by absorption, emission and naked-eye detection methods in organic and aqueous media. Both sensors 4a-b showed selectivity to detecting of CN− besides other interference anions (F−, AcO− and H2PO4−) in aqueous solution. The sensing mechanism of the sensors were investigated by reversibility and 1H NMR titration studies and also supported by DFT calculations. Moreover, LOD values of 4a-b were calculated and the results can be used to detect CN− at a concentration lower than the WHO guideline (2.7 mM) for cyanide. Thermal studies of the compounds have shown that the 4a-b have enough thermal stability properties for application as optic dye. The compound 4b was fully spectroscopically characterized and its structure was unambiguously determined by single crystal X-ray crystallography.