Deltocephalinae is currently the most diverse subfamily of leafhoppers, containing over 6000 described species and nearly 1000 genera. Recent phylogenetic analyses of Cicadellidae based on morphological and molecular data and more detailed analyses of Deltocephalinae and related subfamilies based on morphology have shown that Deltocephalinae is polyphyletic. Members of nine subfamilies recognized in the most recent comprehensive classification of leafhoppers appear to be derived from within Deltocephalinae. However, these previous analyses either had very limited taxon sampling or resulted in low branch support. Thus, the current understanding of relationships in this group is incomplete. The purpose of this analysis is to expand taxon sampling and to add molecular data to the existing morphological data set to obtain a more robust phylogeny that can be used to readdress the higher classification of the group and to infer evolutionary patterns of host plant use. 119 morphological characters, ~2700 bp of the nuclear 28S rDNA gene region, and 353 bp of histone H3 nuclear protein coding gene were assembled and analyzed for 113 taxa. Parsimony and Bayesian analyses of the combined data yielded trees that are generally consistent with previous phylogenetic estimates of the group. The molecular data contributed strong support for many nodes and suggested some relationships that were not supported by morphology alone. Specialization on grasses and sedges occurs ubiquitously in at least 12 tribes, and is shown to be a highly conservative trait. The resulting phylogeny will be used to inform a revised tribal and generic classification of the subfamily.