Two new hyphomycetes, Paradictyoarthrinium aquatica and P. hydei were collected and isolated from submerged wood and decaying wood in China and Thailand respectively. Morphologically, they line well with Paradictyoarthrinium in having superficial, gregarious, black, powdery fruiting bodies, macronematous conidiophores with unevenly dictyoseptate, muriform, subglobose to ellipsoidal dark brown conidia, but they differ from the other species in having short conidiophores. Phylogenetic analysis of combined LSU, ITS and RPB2 sequence data showed that six taxa of Paradictyoarthriniaceae, including the two new species, form a monotypic clade among the phylogenetically close families in Pleosporales with good support. Six isolates of Paradictyoarthrinium formed four distinct clades and represent four different species. Detailed descriptions and illustrations of the new species are provided, as well as the comparisons with related taxa.