Pseudoderbesia eckloniae Huisman & Verbruggen, sp. nov., is described for specimens collected from Cape Peron, Western Australia, growing epiphytically on the kelp Ecklonia radiata (C.Agardh) J.Agardh. The new species forms a velvety turf on the host and is distinguished from related species by a combination of molecular analyses (rbcL) and morphological characteristics.