Invasive plant species pose a threat to the diversity of natural habitats. The extent of the changes depends, among others, on soil properties, settlement time and the degree of coverage of sites by an invasive species. The objective of this study was to determine changes in the habitats of Solidago canadensis at two localities in Poland that differ in soil fertility and acidity. The content of organic carbon, nitrogen and phosphorus, as well as pH were analysed from soil samples collected from the sites invaded by S. canadensis and from the control sites. The composition and species richness of vascular plant communities at the same sites were also determined. The analyses revealed an increase in the soil organic carbon content and in the C/N ratio at the sites invaded by S. canadensis. The presence of S. canadensis also reduced the number of vascular plant species, mainly annuals and perennials. Thus, an increase in S. canadensis cover results in soil degradation and habitat homogenization.