A series of Gd2Ti2O7/In2O3 heterojunction-based composite photocatalysts was prepared by using solid-state reaction methods and their activity was evaluated by measuring the photocatalytic H2 production under visible light (λ≥400 nm). The materials were characterised by using XRD, diffuse reflectance UV (DRUV)/Vis spectroscopy, TEM, field emission SEM (FESEM), photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), and BET surface area and photocurrent measurements. The modification of Gd2Ti2O7 with In2O3 resulted in a remarkable enhancement of the activity for H2 production with respect to the single components under visible light. The photocurrent and Mulliken electronegativity results show that Gd2Ti2O7 and In2O3 have a well-matched band potential to exhibit synergic effects. The enhanced activity may be ascribed to the light absorption properties and the reduction of the recombination of charge carriers at the composite interface. The catalyst Gd2Ti2O7/In2O3 with 60 at % In (60 IGTO) showed the highest activity in comparison to the other composite materials prepared.