Females have a wingspan reaching of up to 16 cm, males are usually a few centimeters smaller. A closely allied species, the New Guinea or Priam's Birdwing (Ornithoptera priamus) reaches 19 cm and is the largest butterfly species found in Australia, but it is not endemic.
Males have a predominately black upper wing with emerald green flashes, however the female lacks the green coloring, having a plain black upper wing with white patches. The female is the larger of the two sexes. The larvae or caterpillars of this species breed on several species of pipe vine, including Aristolochia tagala and Pararistolochia deltantha.