The present study deals with the species of sipunculans collected in the seagrass patches Thalassia hemprichii (Lin, 1998) from Taiwan and two vicinity islands between 2006 and 2007. A total of 10 sipuncula species and 42 specimens belonging to 3 families were identified. Four species: Siphonosoma rotumanum, Siphonosoma vastum, Phascolosoma (Phascolosoma) scolops, and Aspidosiphon (Paraspidosiphon) laevis are reported for the first time from the Taiwan coast. The highest density of sipunculans was found on Mei Yen Don (at Shiuliuchiu, 0.43 ind.m(-2)) followed by Gui-Wan (at Green Island, 0.21 ind.m(-2)) and Nan-Wan (at Kenting Peninsula, 0.11 ind.m(-2)). The highest number of species and specimens, and the values of diversity- and evenness index were estimated in samples taken from Green Island (Gui-Wan), whereas Kenting (Nan-Wan) and Shiuliuchiu (Mei Yen Don) had the lowest values. In the present study, brief descriptions of the species, and their distributional, reproductive and ecological characteristics are also given.