tau Protein/α-synuclein-IN-2 (Compound 14T) is a tau and α-synuclein inhibitor capable of crossing the blood-brain barrier. It reduces α-synuclein oligomerization in a dose-dependent manner through a thiourea linker structure. In biosensor cells, tau Protein/α-synuclein-IN-2 prevents tau aggregation seed effects. In the M17D neuroblastoma model, this compound exhibits anti-inclusion effects and reduces Aβ plaque formation. tau Protein/α-synuclein-IN-2 shows potential for Alzheimer's and Parkinson's disease research.