This study aimed to assess the diversity, abundance and seasonal dynamics of Ophioniformes wasps collected throughout a year, as recorded in Malaise traps set at the Reserva Ecológica da Universidade Estadual do Mato Grosso do Sul, a Brazilian Savanna area in Aquidauana city, MS. A total of 621 specimens of Ophioniformes belonging to 11 subfamilies, 30 genera and 106 species were sampled. Despite the impressive number of species found, in a pattern of a few relatively abundant species and many rare ones, our data estimate even higher richness, probably between 125 to 165 species in the studied area. The genera Diadegma, Nonnus, Diradops, Meniscomorpha, Syzeuctus, Ophiopterus and Thyreodon are recorded for the first time in Mato Grosso do Sul State. Among the climatic variables evaluated, mean temperature and relative humidity were positively and significantly correlated with richness and abundance. Our data highlights the huge unknown species richness of these parasitoids in Brazil and the need of taxonomic studies efforts in the future.