AbstractMolecular data and culture-dependent methods have helped to uncover the phylogenetic relationships of numerous species of lichenicolous fungi, a specialized group of taxa that inhabit lichens and have developed diverse degrees of specificity and parasitic behaviors. The majority of lichenicolous fungal taxa are known in either their anamorphic or teleomorphic states, although their anamorph-teleomorph relationships have been resolved in only a few cases. The pycnidium-formingLichenodiplis lecanoraeand the perithecioid taxaMuellerella atricolaandM. lichenicolawere recently recovered as monophyletic inChaetothyriales(Eurotiomycetes). Both genera are lichenicolous on multiple lichen hosts, upon which they show a subtle morphological diversity reflected in the description of 14 species inMuellerella(of which 12 are lichenicolous) and 12 inLichenodiplis. Here we focus on the teleomorphic genusMuellerellaand investigate its monophyly by expanding the taxon sampling to other species occurring on diverse lichen hosts. We generated molecular data for two nuclear and one mitochondrial loci (28S, 18S and 16S) from environmental samples. The present multilocus phylogeny confirms the monophyletic lineage of the teleomorphicM. atricolaandM. lichenicolawith theirL. lecanorae-like anamorphs, but places the rest of theMuellerellaspecies studied in two different monophyletic lineages with strong support. The first,Muellerellaspp. 1, is nested within some new lineages of black fungi isolated from different epilithic lichen thalli, while the second,Muellerellaspp. 2, is closely related to theVerrucariales. Based on these results, we reappraise the phylogenetic placement ofMuellerellaand suggest its polyphyly withinChaetothyriomycetidae.