The wingspread range is 3.9 to 4.8 cm. The upper surface of the wings is black with submarginal yellow bands. The underside of the wings is black with a submarginal row of yellow spots on the front wing and a submarginal row of wavy red lines on the hind wing. The body of the adult is black with red dots dorsally on the anterior part of the thorax and red-orange dots laterally on the thorax and coxae. An orange lateral line runs the length of the abdomen.
Eggs are variable from yellow to orange or yellow-brown.
Florida larvae are typically dark brown with black-tipped orange tubercles and have an orange collar. Pupae may be light brown with orange markings or light green with yellow markings. The polydamas swallowtail favors open woods or disturbed areas. There are many flights all year in southern Florida and southern Texas, but they are rare during the winter. Young larvae are gregarious, but become solitary as they mature.