Because of the lack of efficacious treatments for advanced melanoma, new approaches are necessary. Chalcones are contained in fruits and vegetables, and have been suggested to be cancer-preventive. In this study, effects of synthetic chalcone derivatives were investigated especially on the proliferation of human melanoma cells and peripheral blood mononuclear cells (PBMCs). Four out of the 12 synthetic chalcones: 4-trifluoromethyl-4'-methoxychalcone (CH-1), 4-trifluoromethyl-2'-methoxychalcone (CH-3), 3-trifluoromethyl-2',4'-dimethoxychalcone (CH-4) and 3-trifluoromethyl-4'-methoxychalcone (CH-7) exhibited significant antiproliferative efficacies against the cultured cells of the human melanoma cell line A375. CH-1, CH-3, CH-4, and CH-7 induced cell cycle arrest at the S-G(2)/M phase within 24 h after the treatment. CH-3, CH-4, and CH-7 significantly activated caspase-3 at 12 h, subsequently induced apoptosis at 72 h. All chalcones inhibited concanavalin A-induced proliferation of PBMCs dose-dependently. Our results suggest that some methoxy- and/or fluoro-chalcones have antitumor efficacy by inducing apoptosis and the cell-cycle arrest.