Two-dimensional (2D) materials have attracted significant attention for device applications due to their unique structural, electronic and catalytic properties. Here, we have deposited a vertically aligned, highly ordered Pd decorated MnO2 nanowalls directly on a porous anodic alumina (AAO) by reactive sputtering and then it used as a gas sensor without additional processing. The nanowalls sensor shows remarkably high and selective responses to hydrogen gas with low detection range 10–10000 ppm. Our results demonstrate the potential application of Pd decorated MnO2 nanowalls for fabricating highly sensitive and selective gas sensors.