How organisms select their habitats is one of the fundamental questions in ecology. Algal surfaces constitute habitat space which is variable on different spatio-temporal scales for shallow water algal associated benthos. The present study focused on animal assemblages associated with Sargassum thunbergii, one of the commonest intertidal algae around Japanese coasts. Abundances of benthos attached to Sargassum were investigated in relation to morphological characteristics of Sargassum. Our results suggest that algal morphology is an important factor which can affect habitat selection by different benthic organisms in different ways.