The larva feed on a wide range of milkweeds of the genus Asclepias. From these plants they acquire and store cardiac glycosides, secondary plant compounds that protect them from predation. The mating period occurs in the spring, just prior to migration from the overwintering sites. The courtship of D. plexippus is fairly simple and less dependent on chemical pheromones in comparison with other species in its genus.
Courtship is composed of two distinct stages, the aerial phase and the ground phase.
During the aerial phase, the male pursues, nudges, and eventually takes down the female. Copulation occurs during the ground phase and involves the transfer of a spermatophore from the male to female. Along with sperm, the spermatophore is thought to provide the female with energy resources that aid her in carrying out reproduction and remigration. Once they reach their breeding grounds, the females lay their eggs on milkweed host plants. The egg and larval period is temperature dependent and lasts about 2 weeks.