With the increasing requirement of the hydrogen energy storage and chemical reactant, it gets to be emergent to exploit room-temperature high-performance hydrogen sensors. By designing a gasochromic-Pd-WO3/graphene/Si tandem structure, here we report an optoelectronic hydrogen sensor, which is working at the room temperature. In this device architecture, the graphene/Si acts as a photodetector layer by using its photovoltaic property and the tandem Pd-WO3film serves as a hydrogen gas sensing layer by using its gasochromic behavior. While the device is exposed to the hydrogen gas, the transmittance of the Pd-WO3can be tuned, which is synchronously sensed by the graphene/Si photodetector. With this principle, the device can detect the hydrogen gas with the concentration down to 0.05 vol% and the response time less than 13 s and the recovery time less than 43 s. This indicates that it is promising to develop the tandem gasochromic-Pd-WO3/graphene/Si structure for room-temperature high-performance low-cost hydrogen sensors. © 2018 Elsevier Ltd