This article outlines a novel material to enable the detection of hydrogen gas, combining thin-film metallic glass (TFMG), ultrananocrystalline diamond (UNCD), and ZnO nanorods (ZNRs) used as a device for effective hydrogen gas sensing has been proposed. Three sensors were respectively fabricated using structures of pure ZNRs (Z), ZNR/UNCD (DZ), and ZNR/UNCD/TFMG (MDZ). The MDZ device exhibited performance superior to the other configurations, with a sensing response of 34% under very low hydrogen gas concentrations (10 ppm) at room temperature. The MDZ sensor proved very fast in terms of response time (20 s) and recovery time (35 s). In terms of selectivity, the sensors were particularly suited to hydrogen gas. The sensor achieved the same response performance even after two months, thereby demonstrating the stability of the hybrid nanostructures. We postulate that the superior performance of MDZ can be attributed to defect-related adsorption as well as charge carrier density. This paper also discusses the respective energy band model of the heterostructures. Our results indicate that the proposed hybrid ZNR/UNCD/TFMG nanostructures could be utilized in high-performance hydrogen gas sensors.