Debate over the synonymy of the European Plagiochila killarniensis and the Neotropical P. bifaria of P. sect. Arrectae has focused on differences in secondary metabolite composition. The broad morphological species concept of P. bifaria proposed in recent papers has now been tested by comparing nrDNA ITS1 and ITS2 sequences of P. bifaria populations encompassing several different morpho- and chemotypes from the British Isles, Tenerife, Costa Rica, Brazil, Ecuador, and Bolivia, with sequences of other species of P. sects. Arrectae, Rutilantes, and Fuscoluteae. Phylogenetic analyses demonstrate that specimens of P. bifaria form a well supported clade within Plagiochila sect. Arrectae. Sequences of P. bifaria from the British Isles, Tenerife, and Ecuador, representing the “methyl everninate” chemotype, form a well supported subclade within the P. bifaria clade. Sequences of specimens from Costa Rica, Brazil, and Bolivia are placed in the basal part of the P. bifaria clade. The data support a broad species concept of P. bifaria. The different chemotypes do not warrant distinct taxonomic ranks. Plagiochila centrifuga and P. compressula are treated as new synonyms of P. bifaria.