Highly sensitive mixed-potential-type NO₂sensors based on yttria-stabilized zirconia (YSZ) electrolyte and In₂O₃-MoO₃nanocomposite electrode were fabricated. The In2O3 doped with 2%, 5%, 10% MoO₃and pure In₂O₃were synthesized by sol-gel method, and these materials were applied to sensing electrode (SE). The effects of doping amount of MoO₃on NO₂-sensing properties were investigated. It was found that the sensor using In₂O₃sensing electrode doped with 5 wt% MoO₃exhibited larger sensitivity to NO₂in the range of 10-200 ppm than the other sensors using In₂O₃doped with 0%, 2% and 10% MoO₃. The sensor using In₂O₃sensing electrode doped with 5% MoO₃showed high sensitivity (59 mV/decade), good stable and repeatable performance at elevated temperature. The electric potential difference (Delta V) of the sensor varies almost linearly with the NO₂concentrations in the examined range of 10-200 ppm. Moreover, it is noteworthy that the influence of relative humidity on NO₂sensitivities at 500℃is little. Combined with the XRD analysis, XPS analysis, ICP analysis of the sensing materials and modified-polarization curves of the sensors, it could be speculated that the MoO₃, doped to the In₂O₃sensing electrode, plays a significant role in sensing performance, and a possible mechanism for the improvement of NO₂-sensing properties was proposed here.