We successfully prepared multiple gas sensing devices comprising of a thin-film sensor made with mesoporous silica combined In2O3-graphene semiconductor nanocomposite for sensing CO2, O-2, and NH3. We demonstrated that our sensor had high selectivity for CO(2)by recognizing O(2)and NH(3)in the vapor stage with accurate transformation into electrical signals in devices. The mesoporous semiconducting In2O3-GO-SiO2-10% (IGS10) sensor showed quick response/recovery times for detecting gases, including CO2, O-2, and NH3. Compared to In2O3, In2O3-GO (IG), and In2O3-GO-SiO2-20% (IGS20), the mesoporous IGS10 showed superior gas sensing ability due to the implied optimum ratio of the synthesized sample. Finally, we proved a facile, low-cost route to attain the multiple gas sensing devices with the potential for vast application.