Monitoring of harmful nitrogen dioxide (NO₂) gases is very important for industrial fields and to maintain a clean environment. In this regard, it is essential to develop low-temperature operating NO₂ gas detecting devices. In recent years, semiconducting oxide-based heterostructured nanomaterials have received considerable attention in the detection of different types of gases at optimal working temperatures. In this context, the selective NO₂ gas sensing properties of CuO-nanoparticles/ZnO-nanorods based heterostructures are described in this article. The sensing films of CuO/ZnO heterostructures are fabricated using catalyst free thermal evaporation route followed by annealing in air and argon gas, respectively. Information regarding the structure, morphology, and composition of the heterostructured films was analyzed using XRD, Raman, EDS, SEM, TEM, XPS and contact angle techniques, prior to sensing measurements. Gas sensing studies have demonstrated that the thermally evaporated CuO/ZnO heterostructured sensor films detect NO₂ selectively at a lower working temperature of 150 °C. The heterostructured CuO/ ZnO sensor showed a maximum response of 96% at 100 ppm NO₂ with good stability, reproducibility, and reversibility in gas response. The main objective of this study is the interaction of NO₂ gas with heterostructured CuO/ZnO sensing materials, which can be helpful in the detection of toxic gases.