The paper reports findings of a natural invasibility study in constructed Mediterranean grasslands, located in the Greek site of the BIODEPTH project. Three different components of invasibility, i.e. species richness, abundance and rarity of invaders, have been monitored in experimental plots where the resident diversity ranged from monocultures to 18-species mixtures. Invaders’ richness and abundance were negatively correlated to the resident diversity, while the occurrence of rare invaders was strongly positively correlated to the resident diversity. Standing biomass explained also a significant part of the variation of communities’ invasibility. Soil nutrients and structural traits of the constructed vegetation such as the space-filling showed no influence in the definition of the overall pattern of invasibility in these communities. A verbal model of selection of invaders at the neighbourhood scale is proposed to explain these diverging trends of invasibility.