It is a colourful species: the dorsal wing surface is black with a large medial patch of metallic blue that is framed by two bands of white on the forewings.

The ventral wing surface is a dull brown to black with muted bands and small red spots on the proximal margin; total wingspan is 55–60 mm.

Sara longwings are one of several heliconiids exhibiting the unusual practice of pupal mating, in which adult males are attracted to female pupae via the latter's pheromones.

Like other heliconiids, females seek the new growth of passion flower vines to lay their small yellow eggs, in clusters of 10–50.

After pupating (with the chrysalis also found on the host vine and camouflaged like a leaf), the adult retains the toxins and is thus protected from predation.