context: In summary, it's proposed that stacking few-layer Nb2CTx with Ti3C2Tx nanosheets into composite structures is a simple and effective approach to improve the electrochemical performance of Nb2CTx-based films for supercapacitors. The intercalated Ti3C2Tx nanosheets between Nb2CTx layers effectively increase the interlayer spacing of Nb2CTx layers and impede the self-restacking of Nb2CTx nanosheets, which are favorable for electrolyte ions to rapidly diffuse and transport in the hybrid electrodes. The optimized Ti3C2Tx/Nb2CTx films possess enhanced capacitive performance and rate performance. A gravimetric capacitance of 370 F g−1 can be delivered at 2 mV s−1 and 56.1% capacitance retention at a high scan rate of 200 mV s−1. The energy density of the assembled all-solid-state supercapacitors can reach 5.5 mW h g−1 at a power density of 141.4 mW g−1, and 1.1 mW h g−1 at a high power density of 2350.0 mW g−1. The all-solid-state supercapacitors presented good flexibility and long cycling life. The all-solid-state supercapacitor was also integrated with a flex sensor to fabricate a self-powered device, where the all-solid-state supercapacitor served as a stable power source unit to drive the flex sensor. The route to fabricate Ti3C2Tx/Nb2CTx hybrid films is also applicable for other M2CTx MXenes, for example, Ti2CTx and V2CTx, improving the application potential of MXenes in flexible supercapacitors and integrated electronic devices.