Herein, efficient synthesis and photophysical study of three novel dyes based on 3‐(isoxazol‐5‐yl)coumarins were developed, and their structures were confirmed by X‐ray crystallography. The access to these fluorophores implied two condensation reaction steps under microwave conditions, starting from 3‐acetylcoumarins and ending with the cyclization of the respective β‐enaminone intermediate with hydroxylamine hydrochloride. By investigating solvatofluorochromism, acidochromism, and properties in the solid state, it was possible to establish that the optical properties of these dyes are coumarin ring‐dependent, which was supported by TD‐DFT calculations. In addition, fluorescence quantum yields (ΦF) up to 36% with short lifetimes decay (1.40–4.60 ns) were accompanied by a redshift behavior with electro‐donating coumarins. Remarkably, solid‐state studies showed a higher emission of the unsubstituted coumarin (ΦF = 64%) due to significant supramolecular interactions; in addition, acidochromism experiments using TFA were performed, finding detection limits of up to 1.03 µM.