The Saint Helena butterflyfish has a silvery-white body with a vertical black band running through the eye.

[1][4] The Saint Helena butterflyfish is a common species of the shallow waters where it occurs.

The juveniles of Thalassoma sanctaehelenae have been recorded acting as a cleaner fish, picking the parasites off this species.

[3] They frequently gather in shoals to feed on refuse tipped into the Saint Helena harbour.

[2] The Saint Helena butterflyfish was first formally described 1868 by the German-born British zoologist Albert Günther (1830-1914).