The detection of chemical warfare agent (CWA's) in real time is obligatory in order to ease the threatening effect of these acute toxic agents to humankind. Herein, firstly we attempted, reversible, colorimetric, and fluorescent detection of phosgene in aqueous system succinctly described based on cyanine scaffold. Rapid and dual response of the probe was constructively employed to monitor the phosgene in the environment by strip test and soil analysis. The probe provides up to ppb (LOD of 0.08 ppb) level detection of phosgene with distinct color and fluorescence change. The turn-on near-infrared (NIR) fluorescence response bring in to play effectively to image trace level phosgene in live cell by fluorescent bio-imaging application.