Hybrid nanostructures made of gallium oxide (Ga2O3) and reduced graphene oxide (rGO) are synthesized using a facile hydrothermal process method, where the Ga2O3 nanostructures are well dispersed on the rGO surface. The formed Ga2O3-rGO hybrids are characterized via Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), a diffuse reflectance Ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer, Brunauer-Emmett-Teller (BET), and photoluminescence (PL). Gas chromatography mass spectrometry (GC-MS) was used for analyzing volatile organic compounds (VOCs). The photocatalytic activity of the hybrid nanostructures is evaluated via the degradation of the 2-butanone, representing the VOCs under 254-nm radiation in the atmosphere. That activity is then compared to that of the Ga2O3 and commercial TiO2-P25. The Ga2O3-rGO hybrid shows enhanced photocatalytic degradation of 2-butanone compared to Ga2O3 and TiO2-P25, which is attributed to the enhanced specific surface area. The results indicate that the Ga2O3-rGO hybrid could be a promising method of enhancing photocatalytic activity and thereby effectively degrading VOCs, including the 2-butanone.