In this study, novel Gd/TiO2@rGO (GTR) nanocomposites with high photocatalytic performance were fabricated via a one-pot solvothermal approach. During the preparation step, graphene oxide (GO) was reduced to reduced graphene oxide (rGO), and subsequently, on the surfaces of which anatase TiO2 doped with Gd metal was grown in situ with a 3D petal-like structure. Gd doping into the classical TiO2@rGO system efficiently expands the absorption range of light, improves the separation of photogenerated electrons, and increases the photocatalytic reaction sites. The specific surface areas, morphological structures, and valence and conduction bands of the obtained GTR nanocomposites were analyzed and correlated with their enhanced photocatalytic performances for the degradation of an aqueous RhB solution. The experimental results indicated that the best performance was achieved with the 3% GTR composite, which exhibited the highest photoelectrocatalytic activity because of two aspects: the rapid separation of electrons and holes, and improvement in adsorption capacity. As compared with pure TiO2, the GTR composites demonstrated enhanced photoactivity due to synergetic effects between the effective photo-induced electron transfer from TiO2 to the surface of the rGO acceptor through interfacial interactions and the variation of structure and electrons under the adoption of Gd.