The braconid subfamily Euphorinae is a large, cosmopolitan group of endoparasitoid wasps. The majority of species attack adult hosts, a strategy that is rare among parasitic wasps, but there are also many species that attack nymphs and larval stages. Euphorine hosts may belong to a variety of insect orders (Coleoptera, Hemiptera, Hymenoptera, Neuroptera, Psocoptera, Orthoptera and Lepidoptera) although most euphorine tribes are confined to Coleoptera. Here we investigate the phylogenetic relationships of the Euphorinae based on molecular data (3 kb of nucleotide data from four markers: 18S, 28S, CAD and COI) and revise their higher-level classification. We also infer the evolution of host associations, and discuss the diversification of the Euphorinae. Results from both Bayesian inference and maximum-likelihood analysis show that the subfamily, as previously circumscribed, is paraphyletic. We propose that the subfamily be expanded to include the tribes Meteorini and Planitorini (Mannokeraia+Planitorius), so that it corresponds to a clade that is strongly supported as monophyletic in our analyses. Based on our results, a revised higher classification of the Euphorinae is proposed, in which 55 extant genera and 14 tribes are recognized. We reinstate the genus Microctonus belonging to the tribe Perilitini and propose the following tribal rearrangements: Spathicopis and Stenothremma are transferred to Perilitini; Tuberidelus, Sinuatophorus and Plynops to Cosmophorini; Ecclitura and Napo to Dinocampini; Chrysopophthorus and Wesmaelia to Helorimorphini; and Proclithoporus to Townesilitini. The monotypic tribes Cryptoxilonini and Myiocephalini are synonymized with Cosmophorini and Syntretini, respectively. The genus Pygostolus, previously placed among the Centistini, is established as its own tribe Pygostolini. Parsimony-based ancestral state reconstructions suggest that the ancestor of Euphorinae was a parasitoid of coleopteran larvae, and that a host shift to larval Lepidoptera occurred early in the evolution of the Meteorini. In the remainder of the subfamily, there was an initial shift from larval to adult coleopterans, followed by subsequent shifts to adults or larvae of Hemiptera, Hymenoptera, Neuroptera, Orthoptera and Psocoptera.