Brain tumors are among the most fatal and devastating diseases, and the lack of effective diagnosis and treatment methods leads to poor prognosis, recurrence-prone, and low patient survival. So far, many researchers have dedicated to develop noninvasive high-resolution imaging to obtain anatomical structures and information about brain tumors, to achieve precise early diagnosis, and to develop novel and efficient therapeutic methods, as well as all-in-one theranostic nanoplatform. Rare earth-based nanoparticles (RENPs) have been widely used in the fields of disease diagnosis, drug delivery, tumor therapy, and bio-imaging, etc. RENPs with unique optical, magnetic properties and high X-ray absorption can be applied for high-resolution imaging of brain tumors by fluorescence imaging, magnetic resonance imaging, and computed tomography imaging. The emission spectrum of RENPs is characterized by low absorption, low photon scattering, and low autofluorescence interference, especially in the NIR-Ⅱ band (Second near-infrared, 1000~1700 nm), which has deep tissue penetration and is suitable as exogenous stimulation for light-responsive therapy. Importantly, RENPs also exhibit low toxicity, biocompatibility, and facile surface functionalization for binding to biomolecules such as antibodies, peptides, and drugs to enhance the ability to cross the blood-brain barrier, which favors targeting therapy and high-contrast imaging. Therefore, this review focuses on the design strategies and applications of rare earth-based materials in the field of brain tumor imaging and therapy, and finally discusses the challenges of RENPs in tumor diagnosis and treatment and provides an outlook on their future development. [ABSTRACT FROM AUTHOR]