This study aimed to develop a high-performance hydrogen flexible sensor based on multi-walled carbon nanotube (MWCNT):SnO2 material. The MWCNT:SnO2 thin film was deposited onto a flexible polyimide substrate by the electron-beam deposition method to perform the low temperature detection of hydrogen. The thickness and surface morphology of the sensing layers have been determined by the thickness measuring profilometer and the scanning electron microscope (SEM), respectively. The flexible MWCNT:SnO2 sensor exhibited excellent sensitive characteristics to hydrogen in a range of 25–3000 ppm. H2 sensing parameters like sensor response, recovery, and response times were investigated at different operating temperatures. The minimum response and recovery times of the sensor corresponding to 1000 ppm H2 concentrations were found to be 37 and 554 s, respectively. The investigated sensing parameters demonstrate that this work can provide the possibility of a versatile route to fabricate flexible hydrogen sensor with high sensitivity and selectivity, which demonstrates its great potential in hydrogen leakage monitoring.