A mixed-potential type solid-electrolyte (MPSE) NO sensor working at room-temperature is of great significance for reducing the power consumption and expanding its application. However, the low sensitivity of the MPSE sensor at room temperature is an urgent problem to be solved. Herein, a highly sensitive room-temperature MPSE NO sensor based on K2Fe4O7 electrolyte and Ni-MOF (coordinated with 1, 4-H2BDC)/MWCNT compound sensing electrode (SE) was reported. Superior NO sensing performances (sensitivities: − 68.0 mV/ppm in 20–500 ppb and − 55.1 mV/decade in 0.5–1 ppm, low detection limit (LOD): 20 ppb, speedy response and recovery rates: 19 s and 25 s) were demonstrated at 25 ◦C. Moreover, with the introduction of MWCNT into Ni-MOF-SE, the MPSE sensor’s response to 500 ppb NO (25 ◦C, 60%RH) has a threefold increase from − 8 mV to − 34 mV. The exciting sensitivity benefits from the enlarged electrochemical active area (ECSA) and improved electrocatalytic activity. This novel and efficient sensitization strategy provides a new idea for constructing highly sensitive room temperature MPSE sensors.