Sabellaria alveolata (Linnaeus, 1767), commonly named “sandcastle worm” or “honeycomb worm”, is a gregarious tube-dwelling polychaete building tubes by assembling sand grains and shell fragments with a proteinaceous adesive. The tubes are closely aggregated to form large reefs. These bio-constructions, providing shelter and food to several reefdwelling species, represent a valuable habitat for benthic invertebrates. For this reason, Sabellaria reefs are listed under Annex I of the EC Habitats Directive as a marine habitat to be protected by the designation of Special Areas of Conservation. Sabellaria alveolata reefs are usually intertidal, and sometimes subtidal, at temperate latitudes and they are commonly recorded in the NE Atlantic coast, from Bristol Channel to the Portuguese coast. Reefs are also found in the Mediterranean Sea, where they are usually smaller and less studied than the Atlantic ones. The aim of this study is to improve the knowledge of S. alveolata structures and associated fauna in the Mediterranean area. Reef samples were collected at three Sicilian sites (Sicily Channel), photographed and stored in absolute ethanol. After sorting, the collected specimens were identified at species level and counted. The morphological analysis was integrated by molecular analyses (DNA Barcoding) aimed at confirming the identity of some species of particular interest. Both analyses confirm the presence of two congeneric species in the reefs: S. alveolata, the dominant species, and S. spinulosa. The rest of the associated fauna was mainly composed by other polychaetes and crustacean amphipods. Among the most abundant polychaetes, Eulalia ornata Saint-Joseph, 1888 (Phyllodocidae) resulted new for the Mediterranean Sea. The Mediterranean Sabellaria reefs are a peculiar habitat not yet properly known. Further study would help to better understand the role of S. alveolata as ecosystem engineer and the factors influencing the dynamics of the biogenic reefs in order to promote their conservation.