Noticeably, calix[4]pyrrole (C4P) derivatives have usually been employed to recognize charged species or polar guests through non-covalent supramolecular interactions, but the chemodosimetric approach remains scarce in the literature. In this study, the selective chemodosimetric detection and quantification of hydrazine, a hazardous pollutant commonly used in the industry, was performed using UV-spectroscopy with a repurposed β-dicyanovinyl substituted calix[4]pyrrole sensor. The selectivity of the chemodosimeter towards hydrazine was evaluated in acetonitrile with various nucleophiles (nitrogen-containing compounds and a thiol). In addition, the influence of several parameters (time, water content, and temperature) on hydrazine detection by the sensor was evaluated. This study allows for the sensing of hydrazine with a limit of detection (LOD) of 1.3 mg/L, and a linear response in the 10–1000 µM range. The ability to detect hydrazine with the naked eye has also been demonstrated. This paper reports one of the first chemodosimetric approach employed with calix[4]pyrrole to detect and quantify a neutral molecule, namely hydrazine.