Wild molluscs from five sites and farmed oysters and abalone from one site each along the south coast of South Africa were examined for shell-boring Polydora and Dipolydora. One new species each of Dipolydora and Polydora are described. D. keulderae sp. n. belongs to the D. barbilla / D. bidentata group and was present at all the sites sampled. P. dinthwanyana sp. n. belongs to the P. ciliata / P. websteri group and was recorded only at Haga Haga, the most easterly site sampled. In total, five Dipolydora species (D. cf. armata, D. capensis, D. cf. giardi, D. keulderae and D. normalis) and three Polydora species (P. cf. ciliata, P. dinthwanyana and P. cf. hoplura) were recorded. All but D. normalis bored into mollusc shells and while the rest of the worms showed no host preference, the larger, subtidal Haliotis spp. and Turbo sarmaticus usually hosted the largest number of species at each site. D. normalis and P. dinthwanyana were recorded only at Haga Haga, P. cf. ciliata only at Port Elizabeth and the rest at all the sites. This study extends the known distributions of D. normalis, D. cf. armata and P. cf. ciliata in South Africa.