In this study, we use the chemical vapour deposition trapping method to grow various one-dimensional (1D) indium oxide (In2O3) nanostructures, namely nanorods (NRs), nanoneedles (NNs), and nanowires (NWs). The structural and morphological characteristics of the synthesised nanostructures are analysed using x-ray diffraction and scanning electron microscopy. By comparing the morphology of In2O3 under different growth conditions with previous research findings, we investigate the growth mechanism and the role of gold catalysts. The In2O3 sensor presented a good selection for C2H5OH gas. The NWs-based sensor exhibits a superior response and faster response-recovery rates (50%, and 49 s/343 s) in comparison to the NRs- (45%, and 35 s/339 s) and NNs-based sensors (8%, and 70 s/496 s) when exposed to 200 ppm C2H5OH at 400 °C. Besides, the sensors exhibited good stability under the switch-off reversible cycle. The linear discriminant analysis (LDA) model was effectively used in classifying target gases such as 25–200 ppm C2H5OH, NH3, and CO at the temperature of 350 °C–450 °C. We attribute the NWs-based sensor's better gas-sensing performance to its favourable morphology for gas diffusion and modulation of depletion depth.