Climacium is a small but morphologically distinctive genus (“tree mosses”) with four species distributed primarily in the Northern Hemisphere. Climacium dendroides occurs around the globe at northern latitudes with disjunct populations in Mexico and New Zealand, whereas C. americanum and C. kindbergii are endemic to eastern North America and C. japonicum is limited to eastern Asia. Using nucleotide sequence data from five plastid loci plus the nuclear ribosomal ITS region we assessed evidence for monophyly of taxonomic species and tested the hypothesis that C. americanum and C. kindbergii from eastern North America have a sister group relationship with C. japonicum from eastern Asia. Climacium japonicum is resolved as sister to a clade containing the circumboreal C. dendroides, C. americanum, and C. kindbergii. Climacium americanum and C. kindbergii were not resolved as monophyletic based on sequence data but together they composed the sister lineage to C. dendroides. Geographically disjunct populations of C. dendroides in Asia, Mexico, the United States, and Canada vary at only a few polymorphic nucleotide sites across the three loci. The disjunctive New Zealand plants of C. dendroides are related to Asian accessions.