This chapter presents the negative impacts of eutrophication which are considered in ecological, economic and social categories. The negative impact of eutrophication on basic physical, chemical and biological properties of water is also presented. Eutrophication has a huge impact on water quality, that may constitute a health hazard for the main water consumer—humans. The main health risk factors of eutrophicated waters are presented: favourable conditions for the development of pathogenic microorganisms, disease causative agents, algotoxins and the type of their impact on the humans. Drinking water supply from the sources with a high trophic status poses a high health risk, and not only due to the presence of toxic algae. Technical and technological problems arising in the event of the need to supply the population from water sources with a high trophic level are also discussed. Particular attention was also paid to various problems of removing nutrients from wastewater before its discharge into receiving water bodies. Economic aspects related to losses and costs incurred due to eutrophication are described, as well as the impact of climate change on the development of eutrophication and feedback relationships.