The study presents a PVC membrane-based potentiometric sensor for iron (III) detection, demonstrating impressive selectivity in Fe(III) ion-selective electrodes (ISE). The sensor achieves a detection limit of 4.0×10−7 M and a Nernstian response slope of 19.4 mV per decade change within a concentration range of 7.4×10−7 to 1×10−1 M. Operating efficiently within the pH range of 3.6–10, the sensor maintains its potential divergence-free utility for at least eight weeks and has a rapid response time of approximately twenty seconds. The sensor’s selectivity for Fe3+ ions makes it a robust tool for specific Fe(III) ion detection. The sensor’s reliability and longevity make it a valuable tool for continuous monitoring applications, providing accurate and timely information on the presence of iron ions in diverse settings.