Papilio palinurus has a wingspan reaching about 8–10 centimetres (3.1–3.9 in). The dorsal sides of the wings are covered by a powder of green scales and the background varies from dark greenish to black, with broad bright emerald green metallic bands. The undersides are black with orange, white and blue spots along the edges of hindwings, that show extended tails at the end.

   The green of Papilio palinurus is created by structural coloration, using special microstructures in the wing scales. The iridescent green sheen of the bands of this butterfly is not produced by pigments, but is structural coloration produced by the microstructure of the wing scales. They refract the light and give rise to blue and yellow visible reflections, producing the perception of green color when additively mixed. 

   They do not exhibit any symptoms of sexual dimorphism. Both male and female are of similar size and coloration.

   The dorsal and ventral sides of their wings are markedly different however. The ventral side wing is varying shades of black, with numerous blue, white and orange spots, primarily along the edges of the hindwings.

   These ventral wing colors, are also not produced by color pigments, but rather by light refracted off the wing scales.

   Emerald Swallowtails feed exclusively on nectar, which in turn makes them good pollinators.

   There are six distinct subspecies of the Emerald Swallowtail.

   Each of these subspecies, as well as the Emerald Swallowtail, appears on the IUCN Red List of Threatened Species. Fortunately, they are listed as of Least Concern.
   The flight of these butterflies is quite fast.