Pseuduvaria khaosokensis Yoosukkee & Chaowasku (Annonaceae), a new species from Surat Thani Province, southern Thailand, is described and illustrated. A plastid phylogeny with 55 accessions of Pseuduvaria and six DNA regions (matK, rbcL exons; trnL intron; atpB–rbcL, psbA–trnH, trnL–trnF intergenic spacers) included placed the new species as a sister group to P. setosa, a widespread species occurring in southwestern and southern Thailand, as well as in Peninsular Malaysia. The two species are primarily distinguishable from each other by differences in the indumentum on young twigs and leaf margin, petiole length, leaf base, shape of inner petal glands, number of stamens per male flower, and monocarp shape and surface.