It is a dorid nudibranch, a shell-less marine gastropod mollusk in the family Discodorididae.

[2] This species was described from a single specimen collected at Lifou, Loyalty Islands, by Dr A.

[1] Halgerda willeyi has been reported throughout the western Indo-Pacific, including Taiwan, Vietnam, Myanmar, Egypt, Indonesia, Malaysia and Australia and in the Red Sea.

[3][4][5] The body of the Halgerda willeyi is rigid, with a series of acute interconnecting ridges.

This species is a fairly large halgerdid,[6] and can reach 50 mm.