The spread of species of the alien genus Carpobrotus in Mediterranean coastal ecosystems can produce a wide range of impacts, including changes in community diversity and alterations of the plant-soil relationships. We focus on the role played by the type of invaded habitat in determining the intensity of soil modifications by Carpobrotus. We hypothesize that there are significant differences between invaded and non-invaded soil parameters and that the intensity of the modification depends on the type of invaded habitat. We selected a test area on the Tyrrhenian coastal dunes of Central Italy (Circeo National Park) for the analyses. We sampled soils in paired invaded and non-invaded plots in areas invaded by Carpobrotus aff. acinaciformis. Nitrogen content, organic matter content, pH and salinity were measured in three coastal habitats (sensu Habitats Directive): the shifting dunes along the shoreline with Ammophila arenaria (EC Habitat 2120), the Crucianellion maritimae fixed beach dunes (EC Habitat 2210) and the fixed coastal dunes with Juniperus spp. (EC Habitat 2250). For each of the three native habitats, soil parameters of the invaded plots were compared to non-invaded ones using Wilcoxon Signed Ranks Tests. We found significant differences between invaded and non-invaded plots for nitrogen content, organic matter content and pH in both foredune habitats (EC 2120 and EC 2210). On the other hand, no differences were revealed on fixed dunes (EC 2250). Further, soil salinity in invaded plots was not significantly different from salinity of non-invaded soils in any of the habitats considered. We found distinct responses of soil parameters to Carpobrotus presence depending on the habitat. Pioneer habitats with very poor soils are more sensitive to Carpobrotus invasion probably because the production of litter by Carpobrotus is considerably higher than for most native species. Since these soil modifications in invaded areas could threaten the native plant diversity, further studies are necessary to better address the problem.