Monitoring gas species and concentrations has been in high demand recently. However, integrated systems with detection of multiple gases still have not been fully explored due to the scarcely developed composite sensing designations. Here, we have demonstrated a Janus mesoporous sensor device that is capable of detecting multiple gases simultaneously based on multi-response mechanisms. The Janus mesoporous devices have shown distinct ultrafast response time, superior selectivity, and ultralow limit of detection in sensing NH3 and H2S at room temperature. Simultaneous real-time quantitative detection of NH3 and H2S can also be achieved by using the difference in response time. Theoretical studies revealed that the distinction of response time is due to the varied interaction of active sites, thus allowing for differentiated multiple sensing signals. Such design of asymmetric architecture represents a new concept for integrated nanostructures toward multi-sensing technologies. Single-gas-phase chemical detections have recently attracted much attention in diverse fields; however, the pathways of composite sensing systems for detection of multiple gases could provoke better substantial potentials, which have not been fully explored due to the deficiency of feasible integrated sensing platforms. Here, we demonstrate a Janus mesoporous sensor device based on multi-response mechanisms, which can simultaneously detect multiple gases. The sensor devices based on Janus mesoporous carbon/silica films with asymmetric mesostructures and disparate active sites (–NH2 and –COOH groups) can be prepared via a solvent evaporation-induced self-assembly and selective functionalization strategy. Such Janus devices have exhibited distinct ultrafast response time under ultralow limit of detection and great selectivity and stability for NH3 and H2S sensing, and each gas concentration can be quantified individually. Theoretical calculation reveals that the distinction of response time is ascribed to the interaction difference to target gases, allowing for distinguished multiple signals.