Abstract: Phylogenetic relationships amongst Copidosoma species, e.g. C. floridanum, C. primulum, C. truncatellum and C. agrotis (Hymenoptera: Encyrtidae) associated with noctuid hosts (Lepidoptera) are inferred from nucleotide sequences of the D2 region of 28S rDNA. Both maximum-parsimony and maximum-likelihood analysis show C. floridanum and C. primulum, associated with Plusiinae and Heliothinae hosts separately, descend from a theoretical common ancestor, while C. truncatellum and C. agrotis associated with Noctuinae are more closer to each other. The D2 region of 28S ribosomal RNA appears potentially useful for understanding phylogenetic relationships in this genus.