MXene is a potential candidate of the sensing electrode for flexible gas sensing devices and has attracted considerable attention. However, two-dimensional (2D) MXene Ti₃C₂T_xnanosheet is liable to stack together and lose the high specific surface area, which limits its gas sensing performance. In this work, a room-temperature flexible NO₂sensor based on three-dimensional (3D) crumpled MXene sphere prepared by ultrasonic spray pyrolysis technology is developed. Then, the properties are further improved by designing 3D crumpled MXene sphere/ZnO composites sensitive electrode with high specific surface area and active sites. The selectivity of the flexible sensing device to NO₂is further highlighted, and the response signal to 100 ppm NO₂improves from 27.27 %–41.93 %, and the recovery characteristic substantially increases from ~30 % to ~100 %. The excellent NO₂sensing properties of 3D crumpled MXene sphere/ZnO are attributed to the high surface area, abundance of edges and defects caused by folding, and the formation of MXene/ZnO p–n heterojunction. This work has introduced an idea to improve MXene gas-sensing properties and helped us to further understand the sensing process between MXene and target gas.