Sertularella gayi is a branching colonial hydroid in the family Sertulariidae.

[2] The main stems of the colony are bright yellow and relatively thick, composed of several fibres adhering to each other at the base, becoming monosiphonic with alternating zooids in the upper part of the colony.

As in Sertularella polyzonias they are bulbous in the basal region, and the margin is quadridentate.

[3] The type locality for this species is the English Channel coast of France, from Pirou and Anneville-sur-Mer.

North-East Atlantic, shallow sublittoral to considerable depths.