Accumulation of misfolded α-synuclein in Lewy bodies and Lewy neurites is the pathological hallmark of Parkinson’s disease (PD). To identify ligands having high binding potency toward aggregated α-synuclein, we synthesized a series of phenothiazine derivatives and assessed their binding affinity to recombinant α-synuclein fibrils using a fluorescent thioflavin T competition assay. Among 16 new analogues, the in vitro data suggest that compound 11b has high affinity to α-synuclein fibrils (K i =32.10±1.25nM) and compounds 11d, 16a and16b have moderate affinity to α-synuclein fibrils (K i ≈50–100nM). Further optimization of the structure of these analogues may yield compounds with high affinity and selectivity for aggregated α-synuclein.