A new naturalized plant, Melanthera nivea (L.) Small, which is native to the Southeastern America, West Indies and Central America, was found naturalized in a disturbed field in southern Taiwan. It is distinct from Melanthera biflora (L.) Wild and Melanthera prostrata (Hemsl.) W. L. Wagner & H. Rob. by plant erect or scandent, stems square, corolla white and only with disc florets in head.