In this report, graphene–gadolinium hydroxide (GR–Gd(OH)₃) nanocomposites have been prepared using the hydrothermal process. The crystalline structures of GR–Gd(OH)₃ have been determined by X-ray diffraction (XRD) measurements and their morphologies have been revealed by field-emission scanning electron microscopy (FE-SEM) observations. The optical properties of GR–Gd(OH)₃ have been examined by UV-vis and Fourier transform infrared (FTIR) measurements which revealed mutual interactions between GR and Gd(OH)₃. GR–Gd(OH)₃ was used to modify the glassy carbon electrode (GCE) which was subsequently utilized for electro-oxidation of ascorbic acid (AA) by cyclic voltammetry method. It was found that the electro-catalytic behavior of GCE modified by GR–Gd(OH)₃ (GCE/GR–Gd(OH)₃) was superior to that of the bare GCE. The catalytic oxidation peak current showed a linear dependence on the AA concentration and a linear calibration curve was obtained in the concentration range of 0.1–2.5 mM of AA with the lowest limit of detection (LOD) of 0.06 mM. Simultaneously, the oxidation peaks of AA over GCE/GR–Gd(OH)₃ shifted to lower over potential compared to that of GCE modified by Gd(OH)₃ (GCE/Gd(OH)₃). The results indicate that GR–Gd(OH)₃ can be used as a promising electrode modifier, which offers a new promising platform for application of the rare earth compound in electrochemistry and bioelectronics. Synchronously, the controlled synthesis of GR–Gd(OH)₃ opens an efficient and facile strategy to design other GR-based, rare earth-containing nanocomposites.