We developed self-heated, suspended, and palladium-decorated silicon nanowires (Pd-SiNWs) for high-performance hydrogen (H-2) gas sensing with low power consumption and high stability against diverse environmental noises. To prepare the Pd-SiNWs, SiNWs were fabricated by conventional complementary metal-oxide-semiconductor (CMOS) processes, and Pd nanoparticles were coated on the SiNWs by a physical vapor deposition method. Suspended Pd-SiNWs were simply obtained by etching buried oxide layer and Pd deposition. Joule heating of Pd-SiNW (<1 mW) enables the detection of H-2 gas with a faster response and without the reduction of sensitivity unlike other Pd-based H-2 gas sensors. We proposed a H-2 sensing model using oxygen adsorption on the Pd nanoparticle-coated silicon oxide surface to understand the H-2 response of Joule-heated Pd-SiNWs. A suspended Pd-SiNW showed a similar transient sensing response with around four times lower Joule heating power (147 mu W) than the substrate-bound Pd-SiNW (613 mu W). The effect of interfering gas on the Pd-SiNW was investigated, and it was found that the Joule heating of Pd-SiNW helps to maintain the H-2 sensing performance in humid or carbon monoxide environments.