Currently, most triethylamine gas sensors show long recovery times and poor stabilities, which are not conducive to the application of TEA sensors. Therefore, it is necessary to produce TEA sensors with high response values and fast response and recovery speeds. In this work, we have prepared unique nest-type Fe-doped NiO by a facile hydrothermal reaction with an annealing process. The 0.52at%Fe-doped NiO-based sensor showed significantly improved triethylamine gas performance compared with the pure NiO sensor. The response value for 50 ppm TEA was up to 64, which was about 21 times higher than that of the pure NiO sensor at the same optimum operating temperature of 260 °C. It exhibited a quick response (26 s) and recovery time (5 s), lower detection limit, good selectivity and stability. The fast recovery time (5 s) compensated for the disadvantages of most TEA sensors. Combined with the high response value, the results indicated that the as-prepared nest-type Fe-doped NiO can be used as an ideal material for the effective detection of TEA. Finally, the growth mechanism and improved gas sensitivity mechanism of the Fe-doped NiO was explored in detail.