Wrack made of marine macrophytes accumulated along many Mediterranean beaches plays relevant ecological roles in coastal environments such as providing habitats and nutrients to a variety of organisms and protecting coastline from erosion. Wrack deposits are also considered as reference habitats subjected to mandatory conservation and protection within the Barcelona Convention. Nevertheless, they are deemed as a nuisance by beachgoers and often moved from beaches to adjacent embryo dunes, an important coastal habitat included in the European Directive. But the possible impact of such practice on the development of plants involved in dune formation processes and stability has not been examined. Here, field experiments were used to test the effects of placing Posidonia oceanica wrack layers of different thickness (2, 4 and 8 cm) and composition (wrack without or with sand) on the toe of embryonic dunes on the survival of already established seedlings and on the recruitment success and growth of new seedlings. Thinopyrum junceum, Euphorbia paralias, and Cakile maritima were used as model species. The placement of the thickest wrack layer reduced drastically (up to 70%) the survival of established seedlings, regardless of the species and wrack composition. Wrack also decreased seed recruitment success more than 50%. The thickest wrack layer reduced the growth of newly emerged seedlings of T. junceum (aboveground organ height) and E. paralias (aboveground biomass) while favoured that of C. maritima ones (total biomass). These findings suggest that placing beach-collected wrack at the base of dunes can hinder their colonization by plants, thus questioning about the ecological sustainability of this practice. Coastal managers should be aware that repeatedly moving wrack from the coastline to dunes could ultimately undermine the resilience of these habitats.