: Today, the development of multifunctional nanoplatforms is more seriously considered in the field of cancer theranostics.: In this respect, nanoparticles provide several advantages over the routine, conventional diagnostic methods, and treatments. Due to the expedient properties of iron oxide nanoparticles, such as being readily modified, great payload potential, intrinsic magnetic qualification, considerable biocompatibility, and overwhelming response to targeting strategies, these nanoparticles can be considered good candidates for application as diagnostic contrast agents and drug/gene delivery vehicles, while also being incorporated into hyperthermia-based approaches. Interestingly, these agents are detectable with routine imaging modalities such as magnetic resonance imaging.: Therefore, combining the traditional diagnostics and therapies with nanotechnological approaches may leave a positive impact on the survival rate of patients with cancer. This review summarizes the application of magnetic iron oxide nanoparticles in both and models of brain tumors.