A double wall carbon nanotube (DWNT)-based sensing device was fabricated and tested for hydrogen gas sensing. The DWNT devices have potential improvement in mechanical and thermal resistance due to their double layer structure. DWNTs were used to build a percolation pathway for charge transport and were decorated with a layer of palladium (Pd) nanoparticles of 1, 3, and 6 nm. The effect of nanotube content and Pd nanoparticle layer size on hydrogen sensing performance at room temperature was evaluated. The DWNTs and the nanostructured sensing element were characterized using high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and Raman spectroscopy. DWNT-based nanostructures behave similar to SWNT-based hydrogen sensors despite the known ambipolar behavior that is absent in SWNT devices. © 2012 Elsevier B.V. All rights reserved.