AbstractEarly diagnosis can effectively improve the survival of glioblastoma multiforme (GBM). A specific imaging technique that is simultaneously deep penetrating and sensitive to small tissue changes is desired to identify GBM. Due to its excellent features in signal contrast, detection sensitivity, and none or little attenuation in tissue, magnetic particle imaging (MPI) possesses great potential in cancer diagnosis, especially when the imaging modality is equipped with specifically targeted nanoprobes. However, when gliomas are small, the blood–brain barrier (BBB) is complete and prevents nanoprobes from entering the brain, which negates the theranostic effect. This study proposes a biomimetic nanoplatform that assist the MPI tracers in breaking through the BBB and then demonstrate a targeted and sensitive diagnosis of GBM. Afterward, the photothermal therapy and immune regulation show an excellent therapeutic effect on the GBM. It is experimentally confirmed that the MPI signal does not decay with tissue depth and shows excellent sensitivity for thousands‐cells. Only small animals are conducted in this study due to the limitations of the current commercial MPI scanner, however, this research theoretically enables large animal and human studies, which encourages a promising pathway toward the noninvasive diagnosis of early‐stage GBM in clinics.