<p>Cellular senescence, driven by the interaction between FOXO4 and p53, is increasingly recognized as a crucial mechanism in brain aging and the development of neurodegenerative disorders. The senolytic peptide FOXO4-DRI, which has been thoughtfully designed, selectively disrupts the FOXO4-p53 complex, inducing apoptosis in senescent cells while preserving healthy tissue. In aged mammalian models, administering FOXO4-DRI decreases the accumulation of senescent cells, restores cerebral blood flow and the integrity of the blood–brain barrier (BBB), reverses hippocampal atrophy, and enhances cognitive function. Furthermore, in models of Alzheimer’s disease (AD) and tauopathy, this intervention eliminates amyloid-β and pathological tau, leading to improved memory performance. Preliminary human studies involving FOXO4-axis modulators, such as high-dose fisetin, show a reduction in the senescence-associated secretory phenotype (SASP) and enhancements in cognitive and physical measures among older adults. These findings collectively identify the FOXO4-p53 axis as a potential pharmacological target in brain aging and highlight senolytic therapy as a promising strategy for altering diseases to postpone or reverse age-related cognitive decline. This review consolidates recent findings indicating that FOXO4-dependent senescence significantly contributes to neuroinflammation, synaptic dysfunction, and impaired neurogenesis in the aging brain.</p> Graphical Abstract <p></p>