We report a novel route for enhancing the humidity resistance of SnO2 nanowires (NWs; widely used metal oxide semiconductor gas sensors) based on their coating with a humidity-resistant nanomembrane. A conformal thin film was deposited by Molecular Layer Deposition (MLD) on the SnO2 NWs using trimethylaluminum and ethylene glycol as precursors (100 MLD cycles), followed by oxidation in air at 400 °C. In conditions of increasing relative humidity, the SnO2 NW gas sensor coated with a microporous, 10-nm thick nanomembrane layer of converted alucone obtained by MLD and calcination showed a remarkable gas response compared with the pristine SnO2 NW gas sensor. This sensor was stable and displayed good recovery times in humid conditions (30 and 90% of relative humidity). This work shows the benefits and the practical application of MLD-prepared nanomaterials. This original strategy applied to NW-based gas sensors paves the way for other complex 3D designs and different applications that require gas or ion selectivity, such as photocatalysts and biosensors, in humid atmosphere.