In this study the promoter effect of Ga2O3 in Cu-based catalysts for the methanol steam reforming reaction was examined. Ga-promoted Cu-based catalysts which had shown high performance in the CO2 hydrogenation to methanol were studied in the methanol steam reforming at 493 K-593 K using CH3OH/H2O = 1/1.3 (mol/mol). Cu–Ga/ZnO at 593 K showed high catalytic performance to produce clean hydrogen. In situ DRIFTS-MS experiments of methanol steam reforming and CO2 hydrogenation were performed over Cu–Ga/ZnO catalyst. A relationship between both processes is proposed through common surface formate species.