Tetratheca plumosa R.Butcher sp. nov., was was collected from private property near New Norcia in 2007 and confirmed to be a new species in 2008. This species is closely allied to T. similis Joy Thomps., but differs significantly in having elongate, plumose, gland-tipped hairs on the ovary. Tetratheca plumosa is described herein and its affinities discussed. Illustrations and a distribution map are provided.