This paper presents a hydrogen sensor based on palladium-yttrium (Pd-Y) alloy nanosheet. Zigzag-shaped Pd-Y nanosheet with a thickness of 19.3 nm was deposited on a quartz substrate by using an ultrahigh-vacuum magnetron sputtering system and shadow mask. The ratio of palladium to yttrium in the nanosheet was 0.92/0.08. The fabrication process was simple and low-cost, and the sensor can be mass-produced. The experimental results show the sensor has a superior sensitivity, reversibility, and reproducibility. The resistive-based hydrogen detection mechanism in this research is much simpler and more compact compared to the optical-based detection method. Highlights Pd-Y sensing element was fabricated using a magnetron sputtering system and shadow mask. The Pd-Y compound consisted of 92% Pd and 8% Y. The fabrication process was simple, low-cost, and mass-production compatible. The sensor showed superior sensitivity, reversibility, and reproducibility to hydrogen gas. The device is more compact than the optical-based counterpart.