A hybrid SnO₂ modified multiwalled carbon nanotubes (MWCNTs) gas sensor is developed for the trace level (100 ppb) detection of NO₂ gas at room temperature. A simple method is applied for the synthesis of a hybrid sensor; SnO₂-modified multiwalled carbon nanotubes (MWCNTs), in which MWCNT bundles are uniformly coated in situ with SnO₂ nanoparticles (∼4 nm). The concentration of MWCNTs has been varied and the hybrid MWCNT–SnO₂ sensor prepared using an optimum content of MWCNT (5 mg) is found to exhibit enhanced sensing response characteristics (response = 5.5 × 10³) towards 100 ppb NO₂ gas at a low operating temperature of 50 °C, with comparatively faster response and recovery speeds of 2.3 min and 6.8 min, respectively, as compared to sensor structure based structures based on thin films of pure SnO₂ nanoparticles (response = 1.01 × 10²). The hybrid sensor also exhibits a good response (1.07 × 10³) to 100 ppb NO₂ gas at room temperature. Extensive modulation of the space charge regions formed at the interface of n-type semiconducting nanoparticles of SnO₂ with p-type MWCNTs with interaction to the NO₂ gas along with providing the conducting channels by CNTs for charge carriers are responsible for the enhanced response characteristics of the hybrid sensor.