An intriguing system featuring a wide band gap silica nanowire (SiO xNW) that absorbs visible light (532 nm) via the surface plasmons (SPs) of embedded gold nanoparticles (Au NPs) is reported for sensing applications. We report SP resonance enhanced molecular oxygen sensing by single Au-NPs@SiOx NWs under 532-nm illumination (visible light) at room temperature. Excellent selectivity of the Au-NPs@SiOx NWs to molecular oxygen in air has been demonstrated. Illumination improved the sensing properties in terms of response and fast recovery time, which can be attributed to the photogenerated hole-mediated oxygen desorption. A general strategy of light-modulated sensing, vis-à -vis dark, is demonstrated in a wide band gap single NW system that could potentially open up routes for biosensing, because silica and Au both lack biotoxicity.