Phyllidiella hageni is pink with a variable pattern of black lines on the dorsum. Two longitudinal, black lines run from the rhinophores to the posterior body end. Short, irregular, black lines on the mantle margin. Numerous low and coalesced pink tubercles with white apices are densely scattered on the mantle.
The rhinophores are bicoloured (pink and black), with 19 lamellae.
Seslugs genus Phyllidiella feeds exclisively on sponges.