We report the facile and scalable synthesis of a highly monodispersed inorganic nanostructure based on well-designed Gd(OH)₃ nanorods. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as energy-dispersive spectroscopy (EDS) were applied to characterize the samples, indicating that the nanomaterials with an average length of 100 nm and an average diameter of 15 nm showed a typical hexagonal phase. Biocompatibility tests were performed from in vitro cell experiments to in vivo long-term histological assessment, indicating that the Gd(OH)₃ nanorods were promising for further bio-related application. Owing to the excellent paramagnetic behavior, we further investigated the capability of the nanorods as MRI contrast agent. Compared with the conventional Gd–DTPA complex, the well-designed Gd(OH)₃ nanorods present a higher T₁ relaxation rate, showing more potential for biomedicine applications.