Periconia thailandica is a new hyphomycetous species found on bamboo culms collected in Kamphaeng Phet, Thailand. We herein introduce P. thailandica based on morphological characters and molecular analysis. Phylogenetic analyses of combined ITS, LSU and SSU sequence data place the new species in Periconia (Pleosporales) where it forms a distinct clade in the genus. The new species is characterized by brown, 4−7-septate conidiophores with terminal, polyblastic, acropetally proliferating, globose conidiogenous cells, and light to dark brown, globose, verrucose conidia. The morphological comparisons between P. thailandica and other known Periconia species are discussed. The new species is introduced to accommodate this taxon with a detailed description and morphological illustrations.