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Because of their morphological plasticity and broad geographic distribution, the taxonomy of Dicranum is difficult. The circumscription of the different species included in the Dicranum acutifolium complex is poorly understood and taxonomic confusions are frequent. The present study extends earlier internal transcribed spacer (ITS)-based phylogenetic reconstructions of the D. acutifolium complex by analysing five additional chloroplast markers (trnT– rps4, trnL–F, psbA–trnH, rps19–rpl2, rpoB) together with ITS from a larger taxon sample. The phylogenetic analyses delimit Dicranum acutifolium (Lindb. & Arnell) C.E.O.Jensen, D. bardunovii Tubanova & Ignatova, D. brevifolium (Lindb.) Lindb., and D. septentrionale Tubanova & Ignatova, which together form the D. acutifolium complex, and confirm that D. pseudoacutifolium Otnyukova is synonymous with D. flexicaule Brid. Previously Dicranum septentrionale was known from across Russia, but it also occurs in Scandinavia, where it was probably overlooked due to the morphological resemblance to D. brevifolium. The problem of mixed collections for identification is exemplified by the holotype of D. bardunovii, which also contains individuals of the morphologically most similar D. acutifolium, according to the molecular data. Morphometric analyses support the differentiation of the D. acutifolium complex. Furthermore, ordination analyses point to a continuous range of variation among species within the D. acutifolium complex, especially due to the larger variation in D. septentrionale.