This spherical sponge is typically pale to bright yellow in colour. The surface is tuberculate (warty) and often 'buds' are present, found on short stalks on top of these tubercles. There is one, large compound oscule opposite to the point of attachment. Overall the appearance is like a small orange. Two other species of Tethya, Tethya hibernica and Tethya norvegica are now known from Britain and Ireland. Both are known from very few records. This species may also possibly be confused with Suberites carnosus, however the latter species has a smooth velvety surface. Tetilla cranium and Tetilla zetlandica are the same shape and have a rough surface, but T. zetlandica is bright white and T. cranium has distinctive 'S' shaped microscleres.