In this study, we present a unique technique utilizing POT/SnO2 nanocomposites to create an ultrafast and extremely sensitive nitrogen dioxide gas sensor. Various characterization approaches, including XRD, FE-SEM, UV–Vis spectroscopy, Raman spectroscopy, and FTIR, were systematically applied to verify the successful synthesis of the POT/SnO2 nanocomposite. We tested the conductivity and sensing efficiency with an emphasis on the chemosensitivity component. The sensor based on POT/SnO2 has remarkable sensitivity over a broad range of NO2 concentrations from 5 to 650 ppm. Our results indicate that the incorporation of SnO2 into POT significantly enhanced the sensor sensitivity, increasing from 26% for pure POT to 87% for the composite. This improvement produced rapid response and recovery times of 47 s and 44 s, respectively, along with remarkable long-term stability at room temperature. With its remarkable sensitivity and performance characteristics, our sensor emerges as a strong contender for real-time nitrogen dioxide detection, representing a noteworthy advancement in gas sensing technology.