We tested whether long copulation duration is more likely to have evolved in nonterritorial odonate species than in territorial species, given that nonterritorial males do not incur the costs of territory defense. A phylogenetic comparative method that controls for the phylogenetic nonindependence of species was used to compare copulation duration among 46 species of the two main odonate suborders (Anisoptera and Zygoptera). Copulation duration of nonterritorial anisopteran species was longer than for territorial dragonflies; however, this relationship was not found for Zygoptera. Long copulations in Anisoptera may be related to a male's ability to manipulate a female's stored sperm. It is suggested that constraints that prevent a territorial male from lengthening copulation do not seem to operate in Zygoptera. Other selective processes (i.e., cryptic female choice and/or sexual conflict) may also be important determinants of copulation duration in the Zygoptera. To our knowledge, this is the first exploration of the relation copulation duration and mating systems in insects.