Increased introductions combined with favorable growing conditions may enhance the presence and increase the success of alien plant species in High Arctic settlements. With global warming, the presence and success of alien plants in Polar Regions might expand beyond the confinement of human settlements and cause problems for native species and ecosystems. Presence and abundance of alien and native vascular plant species were recorded, from chosen study sites, in the Svalbard settlements of Barentsburg and Longyearbyen during the summer of 2011. Soil temperature and soil nutrient concentrations measurements were also conducted in the same study sites. The effect of soil temperature attributes and soil nutrient concentrations on alien species, compared to native species, were investigated. Further, the effects of presence and abundance of alien plant species on the abundance of native plant species was investigated. The results indicated that both high soil temperature and high soil nitrogen concentrations may facilitate alien plants in Svalbard settlements. Further, the results showed that both presence and abundance of alien plant species had a negative effect on native species abundance in the study sites. This may imply that when alien plant species are facilitated, they may constitute a threat to native species abundance in High Arctic settlements.