The phenomenon of biological invasions, or the human-mediated movement of non-indigenous species (NIS) to areas where they did not previously occur, increasingly attracts attention not only of scientists, but also environmental policy makers and industry. The study of biological invasions became a complex interdisciplinary scientific research area, which involves both fundamental and applied aspects. The present work is devoted to the analysis of the biological invasions impacts and risk assessment methods, which are needed both for theoretical studies and practical management of biological invasions. At first, the requirements of international and European legislation were analyzed with the aim to develop the criteria and a scoring system for the evaluation of the appropriateness of the bioinvasion impact and risk assessment methods. Then the scoring system based on the key risk assessment (RA) principles, RA components and categories of bioinvasion impacts was applied to evaluate the methods. Another task of this work was to develop and apply the nNIS index, an approach for assessment of the effectiveness of the environmental policy aimed at prevention of the biological invasions. The index is based on a global information system on aquatic NIS (AquaNIS), which completes nNIS with data on introduction pathways, environmental tolerance limits and biological traits of these species. Also, the Mean Expansion Rate (MER) was studied as a measure of species invasiveness, which helps to distinguish between the human-mediated and natural spread of NIS. The combination of the latter two tools may be used for the implementation of the environmental policy on biological invasions, such as the International Convention for the Control and Management of Ship’s Ballast Water and Sediments, the EU Regulation on Invasive Alien Species, the EU Water Framework and Marine Strategy Framework directives.