Controlled amounts of colloidal Au nanoparticles (NPs), electrochemically presynthesized, were directly deposited on MWCNTs sensor devices by electrophoresis. Pristine and Au-functionalized MWCNT networked films were tested as active layers in resistive gas sensors for detection of pollutant gases. Au-modified CNT-chemiresistor demonstrated higher sensitivity to NO2 detecting up to sub-ppm level compared to pristine one. The investigation of the cross-sensitivity towards other pollutant gases revealed the decrease of the sensitivity to NO2 with the increase of Au content, and, on the other side, the increase of that to H2S; therefore the fine tune of the metal loading on CNTs has allowed to control not only the gas sensitivity but also the selectivity towards a specific gaseous analyte. Finally, the sensing properties of Audecorated CNT sensor seem to be promising in environmental and automotive gas sensing applications, based on low power consumption and moderate operating temperature. © 2015 Materials Research Society.