Abstract Recent studies of the phylogeny of several groups of native Hawaiian vascular plants have led to significant insights into the origin and evolution of important elements of the Hawaiian flora. No groups of Hawaiian pteridophytes have been subjected previously to rigorous phylogenetic analysis. We conducted a molecular phylogenetic analysis of the endemic Hawaiian fern genus Adenophorus employing DNA sequence variation from three cpDNA fragments: rbcL, atpβ, and the trnL-trnF intergenic spacer (IGS). In the phylogenetic analyses we employed maximum parsimony and Bayesian inference. Bayesian phylogenetic inference often provided stronger support for hypothetical relationships than did nonparametric bootstrap analyses. Although phylogenetic analyses of individual DNA fragments resulted in different patterns of relationships among species and varying levels of support for various clades, a combined analysis of all three sets of sequences produced one, strongly supported phylogenetic hypothesis. The primary features of that hypothesis are: (1) Adenophorus is monophyletic; (2) subgenus Oligadenus is paraphyletic; (3) the enigmatic endemic Hawaiian species Grammitis tenella is strongly supported as the sister taxon to Adenophorus; (4) highly divided leaf blades are evolutionarily derived in the group and simple leaves are ancestral; and, (5) the biogeographical origin of the common ancestor of the Adenophorus–G. tenella clade remains unresolved, although a neotropical origin seems most likely.