Abstract Progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) are classically associated with 4-repeat tauopathies, but emerging evidence indicates that a subset of patients with PSP-like or CBS-like phenotypes have autoimmune or paraneoplastic etiologies. These immune-mediated mimics can present with subacute onset, atypical features (such as prominent sleep disturbances, seizures, or rapid early progression), and the presence of specific neural autoantibodies. Recognizing these cases is critical, as they are potentially reversible with immunotherapy, unlike the relentlessly progressive course of neurodegenerative PSP/CBD. Here we review the mechanistic overlap between autoimmunity and neurodegeneration, highlight reported cases of autoimmune CBS and PSP mimics (and their characteristic clinical clues), and discuss immunotherapy strategies. While many patients improve with timely immunosuppressive treatment, outcomes vary by antibody type – reflecting direct pathogenic roles for cell-surface antibodies versus bystander phenomena in some intracellular (paraneoplastic) antibody cases. Ongoing research and accumulation of case reports will clarify the true frequency of autoimmune PSP/CBS and optimize their management