The tenebrionid community inhabiting a Mediterranean dune ecosystem (Circeo National Park, central Italy) was analysed to study (1) the distribution and diversity of these beetles in three different plant associations, and (2) the seasonal changes of the community composition and structure. Monthly samplings were made by sieving a fixed volume of sand and detritus. Most species showed a different abundance in the three habitats, and substantial differences were observed in the monthly values of species richness and diversity. A decrease of the overall density was observed from the external to the innermost plant association, characterized by a higher plant cover. The community also showed clear temporal phases, with an overall decrease in winter and summer, confirming a pattern previously observed also in other soil arthropods living in Mediterranean arid environments.