In this work, we investigated the effectiveness of a pre-biasing measurement technique for improving the gas-sensing performance of a metal oxide semiconductor (MOS)-based thin-film transistor (TFT)-type gas sensor for the first time. Various pre-biases voltages were applied to an indium-gallium-zinc oxide (IGZO) TFT gas sensor, and the resulting effects on NO 2 detection performances were examined at various NO 2 concentrations and temperatures. Our results showed that the NO 2 sensing performance of the IGZO TFT sensor could be significantly improved by application of a positive pre-bias voltage to the gate electrode of the IGZO TFT. The impact of pre-bias voltage application was more significant when the pulse amplitude and width were increased, especially at temperatures below 90 °C. Enhancement of IGZO TFT NO 2 sensor performance was attributed to an electric-field-induced chemisorption of NO 2 on the active back channel of the IGZO TFTs during pre-bias voltage application. Our results demonstrated that the pre-biasing measurement technique is a simple and effective biasing scheme that can enhance the gas-sensing performance of three-terminal TFT-type gas sensors that employ MOS for both the channel and sensing layers.