A stable MC (merocyanine)‐spiropyran as p‐toluenesulfonate salt was synthesized. The structure of the merocyanine salt form of the spiropyran was established by using IR, ¹H‐NMR, ¹³C‐NMR, 2D‐NMR and HR‐MS spectroscopic techniques. The MC salt was employed as an optical probe for the detection of trace water content in the organic media using the naked eye, UV‐Visible and fluorescence spectroscopic techniques. The DLS and TEM measurements were used to support the aggregation and disaggregation of the MC salt form. The results established the conversion of H‐ aggregates to J‐ aggregates can be used for the efficient detection of trace water content in organic media. The optical probe was further used to sense and quantify water molecules associated with the metal salts. The probe can be used multiple times for sensing water. The results provide insightful opportunities for practical applications of sensing trace water content in organic solvents and coordinated to metal ions.