Tau Protein/α-synuclein-IN-2 (Compound 14T) is a blood-brain barrier penetrating tau and α-syn inhibitor. Through its thiourea linker structure, Tau Protein/α-synuclein-IN-2 dose-dependently reduces α-syn oligomerization. In biosensor cells, Tau Protein/α-synuclein-IN-2 prevents the seeding effect of tau aggregation. In the M17D neuroblastoma model, Tau Protein/α-synuclein-IN-2 exhibits anti-inclusion effects. Additionally, Tau Protein/α-synuclein-IN-2 reduces Aβ plaque formation. Tau Protein/α-synuclein-IN-2 holds promise for Alzheimer's disease and Parkinson's disease research.