The inability of most therapies to penetrate the blood–brain barrier is a major obstacle contributing to the poor prognosis of glioblastoma. A new review examines next-generation nanomedicines, including stimuli-responsive, biomimetic nanoparticles, that are being engineered to transport therapeutics directly into brain tumors. The authors discuss advances in brain-targeting strategies, externally activated therapies, and biomimetic platforms while outlining the challenges that must be overcome before these technologies can achieve widespread clinical use.