Significance Parkinson’s disease is characterized by the accumulation of amyloid deposits in dopaminergic neurons, mainly composed of the protein α-synuclein. The disordered nature of α-synuclein and its complex aggregation reaction complicate the identification of molecules able to prevent or revert the formation of these inclusions and the subsequent neurodegeneration. By exploiting a recently developed high-throughput screening assay, we identified SynuClean-D, a small compound that inhibits α-synuclein aggregation, disrupts mature amyloid fibrils, prevents fibril propagation, and abolishes the degeneration of dopaminergic neurons in an animal model of Parkinson’s disease.