Gemmula cosmoi is a species of sea snail, a marine gastropod mollusk in the family Turridae, the turrids.

An almost uncolored to slightly brown shell.

It shows a row of tiny nodules on the keel of the whorls.

The suture has a row of pointed nodules.

[2] This marine species occurs from East Africa to Japan; in the East China Sea, South China Sea and Nansha Islands; off the Philippines.