Flexible room-temperature gas sensors with good adaptability to various surfaces and low energy consumption hold a great promise for different applications such as environmental monitoring and human exhalation detection. However, the development of flexible sensing devices with stable and superior monitoring capability is still restricted by the insufficient selectivity or sensitivity at low temperatures. In this study, a simultaneous etching and oxidation polymerization strategy is developed toward the synthesis of porous polypyrrole (PPy)/Ti₃C₂T_x MXene nanocomposites. In the nanocomposites, PPy nanosheets align vertically on the surface of Ti₃C₂T_x, forming numerous open and porous channels. As a result, the PPy/Ti₃C₂T_x-based flexible sensor shows highly exposed active sites and superior ammonia sensing performances at room temperature with good selectivity, high sensitivity, fast response rate, and a low detection limit of 375 ppb. The sensor can exhibit stable and reliable sensitivity under different bending angles and even after 100 bending cycles. Moreover, the PPy/Ti₃C₂T_x nanocomposites can be integrated into a portable flexible wireless sensor for remote and real-time ammonia monitoring, exhibiting great potentials in various applications.