Deltocephalinae, a highly diverse and economically important subfamily of leafhoppers, contains over 6200 species and 36 tribes distributed worldwide in habitats ranging from xeric grasslands and shrublands to tropical rainforests. Recent morphological and molecular phylogenetic analyses of Cicadellidae and a morphology-based analysis of Deltocephalinae and related subfamilies indicated that several previously recognized cicadellid subfamilies are closely related to or derived from within Deltocephalinae, but these analyses did not provide a comprehensive or well-supported hypothesis of the phylogeny of Deltocephalinae s.l. due to either low taxon sampling or low branch support. Here, taxon sampling was increased to include members of most family-group taxa of Deltocephalinae and molecular data (∼2800 bp 28S rDNA and ∼350 bp histone H3) were added to improve the phylogenetic estimate. Five putative outgroup taxa were included, and parsimony and Bayesian analyses of the combined molecular and morphological (119 characters) data and maximum likelihood analyses of the 28S data showed strong support for the monophyly of Deltocephalinae as defined here. Branches near the base of the tree and towards the tips were longer and better supported than many of the shorter internal branches. Similar to a previous morphological phylogenetic analysis of Deltocephalinae, all of the grass- and sedge-specializing tribes were recovered in one common clade, with a few apparent reversals to nongrass feeding. Although support for this clade was low and requires further testing, the results suggest that grass/sedge specialization is a phylogenetically conservative trait within Deltocephalinae. The history of the classification of Deltocephalinae and related subfamilies is reviewed, and based on the results of the phylogenetic analyses presented here, a revised family-group taxonomic classification is proposed. In addition to subfamilies that were recently included in Deltocephalinae, the following are considered junior synonyms of Deltocephalinae: Acostemminae syn.n., Arrugadinae syn.n., Drakensbergeninae syn.n., Mukariinae syn.n. and Stegelytrinae syn.n. The morphological characters supporting this interpretation of Deltocephalinae are provided and discussed, and a description of the subfamily is provided. A new tribe, Faltalini tribe n. (11 genera, 31 species) is described, and Magnentiini placement n. and Paraphrodini placement n. are transferred to Deltocephalinae from Nioniinae and Aphrodinae, respectively. New placements of genera include: Twiningia Ball and Eusama Oman (Athysanini: Platymetopiina), placement n.; Cerrillus Oman (Athysanini), placement n.; Scaphotettix Matsumura and Agrica Strand (Mukariini), placement n.; Loralia Evans and Phlogotettix Ribaut (Deltocephalinae, unplaced to tribe), placement n. The recognition of Scaphoideini Oman 1943 as a nomen nudum results in the following placements: Acunasus DeLong, Cantura Oman, Danbara Oman, Osbornellus Ball, Prescottia Ball, Scaphodhara Viraktamath & Mohan, Scaphoideus Uhler, Scaphoidophyes Kirkaldy, Sincholata DeLong, Sobara Oman and Soleatus DeLong (Deltocephalinae, unplaced to tribe), placement n.