Parasitoids may have important role in the biological control of social wasps. The objective of the current study was to identify and to measure colonies of the social wasp Polistes versicolor Olivier, 1791 (Hymenoptera: Vespidae) that were attacked by parasitoids in the campus of the Federal University of Viçosa in Viçosa, Minas Gerais State, Brazil. The nest cell diameter, maximum and minimum width and height of the colony above the ground were recorded; in addition, the number of nest cells, pupae, larvae and eggs of parasitized colonies was determined in the laboratory from ten colonies of P. versicolor collected between April and May 2011. Parasitoid emergence was monitored on a daily basis. An individual of a non-described species of Pachysomoides (Hymenoptera: Ichneumonidae: Cryptinae) emerged from one P. versicolor colony collected from a plant of the sweet orange Citrus sinensis (L.) Osbeck (Rutaceae). This colony had a nest cells diameter of 0.50 mm, a maximum and minimum width of 5.50 mm and 3.40 mm, respectively, and it was 1.48 m above the ground. In total, 189 nest cells, 19 pupae, 27 larvae and 41 eggs were found in the colony. This is the first report of a parasitoid of the ichneumonid genus Pachysomoides from a colony of the wasp P. versicolor in Brazil.