A hybrid composite Multi-Walled Carbon Nanotube (MWCNT) sheet decorated with a manganese oxide (MnOx) gas sensor was developed for the detection of hydrogen (H-2) gas; electrical resistance increases linearly with H-2 exposure. The MnOx particles were coated uniformly on the MWCNT sheets by electrodeposition, which is simple and controllable for fabricating binary or hierarchical composites. The sensitivity of the sensor was affected by the mean size of the MnOx particles, which in turn were controlled by the electrodeposition time. The measured output characteristics were quite stable, reliable and reproducible. (C) 2013 Elsevier B.V. All rights reserved.