The high sensitivity of room-temperature gas sensors is the key to innovation in the areas of environment, energy conservation and safety. However, metal-oxide-based sensors generally operate at high temperatures. Herein, we designed three ZrO₂-based sensors and explored their NO₂ sensing properties at room temperature. ZrO₂ with three different morphologies and microstructure were synthesized by simple hydrothermal methods. The microstructures of sensing materials are expected to significantly affect gas sensing properties. The rod-shaped ZrO₂ (ZrO₂-R) displayed the advantages such as higher crystallinity, larger pore size, narrower band gap and more chemisorbed adsorbed oxygen, compared to hollow sphere-shaped ZrO₂ (ZrO₂-HS), stellate-shaped ZrO₂ (ZrO₂–S). The ZrO₂-R sensor showed the highest response towards 30 ​ppm NO₂ (423.8%) at room temperature, and a quite high sensitivity of 198.0% for detecting 5 ​ppm NO₂. Although ZrO₂-HS and ZrO₂–S sensors exhibited lower response towards 30 ​ppm NO₂ (232.9% and 245.1%), the response time and recovery time of these two sensors are 5 ​s/19 ​s and 4 ​s/3 ​s, respectively. This work can provide a new strategy for the development of room-temperature metal-oxide-based sensors.