The Ozark swallowtail is almost identical to the black swallowtail. Despite this similarity, an analysis of the Ozark swallowtail's mitochondrial DNA suggests that it is actually more closely related to the Old World swallowtail. On both surfaces of the hindwing, the pupil in the eyespot usually touches the edge of the inner margin. On the underside of the hindwing, the orange spots have very little or no yellow in them. The black adult color pattern characterizing P. polyxenes is presumed to be inherited as a simple autosomal dominant
The caterpillar is morphologically very similar to the black swallowtail caterpillar. The two species may be more easily distinguished by the habitat and host plants upon which the caterpillar feeds, as these differ. There are two broods per year.