For rapid hydrogen gas (H-2) sensing, we propose the facile synthesis of the hollow structure of Pt-decorated molybdenum disulfide (h-MoS2/Pt) using ultrathin (mono- or few-layer) two-dimensional nanosheets. The controlled amphiphilic nature of MoS2 surface produces ultrathin MoS, NS-covered polystyrene particles via one-step Pickering emulsification. The incorporation of Pt nanoparticles (NPs) on the MoS2, followed by pyrolysis, generates the highly porous h-MoS2/Pt. This hollow hybrid structure produces sufficiently permeable pathways for H-2 and maximizes the active sites of MoS2, while the Pt NPs on the hollow MoS2 induce catalytic H-2 spillover during H-2 sensing. The h-MoS2/Pt-based chemiresistors show sensitive H-2 sensing performances with fast sensing speed (response, 8.1 s for 1% of H-2 and 2.7 s for 4%; and recovery, 16.0 s for both 1% and 4% H-2 at room temperature in the air). These results mark the highest H-2 sensing speed among 2D material-based H-2 sensors operated at room temperature in air. Our fabrication method of h-MoS2/Pt structure through Pickering emulsion provides a versatile platform applicable to various 2D material-based hollow structures and facilitates their use in other applications involving surface reactions.