This report develops a coumarin-nicotinic hydrazide-based sensor for detection of CN- ions. The ligand is prepared by simple method and has been characterized by H-1 NMR, C-13 NMR, FTIR, and mass spectral analyses. The sensing behavior of coumarin-nicotinic hydrazide (CNH) probe was investigated in the presence of different anions using UV-visible and fluorescence methods. The sensor showed a selective naked-eye, colorimetric, and fluorescence detection particularly in the presence of CN- ions over the other anions. The sensing involves a ratiometric red shift in absorption and photoluminescence profile in presence of incremental addition of CN- ions. This provides a multi-detection point at two different wavelengths. This sensor involves a displacement type approach through a nucleophilic substitution-based chemodosimeter sensor proposed based on H-1 and C-13 NMR along with D2O exchange experiment, and mass and photophysical studies. Interestingly, the sensor affords the lowest limit of detection up to 5.97 x 10(-7) M. The practical utility of the sensor is illustrated in molecular logic gate operation and real water analysis.