The genus Diolcogaster Ashmead constitutes one of the dominant genera of the Microgastrinae (Hymenoptera: Braconidae). Many systematist doubt the monophyly of this species-diverse genus due to its morphologically diverse species composition. As a result, Diolcogaster is divided into several species-groups, some of which have closer relationships to other genera outside Diolcogaster. The relationships of Diolcogaster and related genera (Buluka, Parenion, Exix, Wilkinsonellus, Deuterixys, Protomicroplitis, Larissimus and several new genus candidates) have hardly been investigated rigorously. In this study, we focus on improving the systematics of the Diolcogastroid complex, Diolcogaster and its related genera, which includes a taxonomic revision of the New World Diolcogaster, improved taxonomy of Diolcogastroid complex, and species- and generic level phylogeny of the Diolcogastroid complex using morphological and molecular data. Resolution of this study should result in a reclassification of the Diolcogastroid complex, and help contribute to a phylogenetically realistic generic classification for Microgastrinae.