Primary and metastatic brain tumors exhibit resistance to immunotherapies that demonstrate efficacy in peripheral cancer settings. While many immunotherapies aim to enhance CD8 + T cell infiltration and functionality in established tumors, identification of neoantigens support emerging immunopreventative tactics against brain cancer. Functionally potent tissue-resident memory CD8 + T cells (T RM ) can be generated in the brain following peripheral infection or vaccination. However, the ability of brain T RM to prevent intracranial malignancy remains unknown. Here, mice were seeded with tumor-specific or bystander brain T RM via peripheral infection prior to depletion of circulating memory T cells (T CIRCM ) and subsequent brain tumor challenge. Tumor-specific brain T RM durably protected mice against intracranial malignancy even in the absence T CIRCM . These brain T RM persisted in tumor-surviving mice and protected against a second antigen-matched challenge. Importantly, a translationally-relevant mRNA-lipid nanoparticle (LNP) vaccine phenocopied peripheral infection-induced outcomes, generating functional brain T RM that controlled tumor growth. Altogether, this work points to the utility of brain T RM in cancer immunoprevention, supporting the development of antitumor mRNA-LNP vaccines to bolster brain immunity.