In this work, a flexible hydrogen (H₂) gas sensor using Pt/Pd bimetal decorated vertical ZnO nanorods (Pt/Pd-ZnO NRs) on polyimide/ polyethylene terephthalate (PI/PET) substrate was studied. The as-fabricated sensor exhibits a high response magnitude of 69.8 (10,000 ppm), fast response time of 5 sec, and broad detection range from 0.2 to 40,000 ppm at 100 °C. The superior sensing performance was mainly attributed to the enhanced hydrogen-induced changes in the work function of the Pt/Pd-ZnO NRs, which was configured as an array matrix and nanorods cluster with a variable distance between the two electrodes. At optimum conditions (3/3 nm Pt/Pd-ZnO NRs at 100 °C), the device did not show significant degradation in sensing performance even when bent to a curvature angle of 90° and after 10⁵ cycles of deformation. Lightweight and mechanically robust Pt/Pd-ZnO NRs could be a promising building block for fast response and stable flexible hydrogen sensors.