The objective of this study was to investigate the impacts of the construction of the Belo Monte Hydroelectric Power Plant on the traditional knowledge of three riverine communities located in the cities of Altamira and Vitoria do Xingu. For that, we interviewed the residents of the communities of Mexicano (Altamira) and Bambu and Belo Monte (Vitoria do Xingu), with the help of questionnaires, applied in November 2016. Participated in the interview 70 people, 37 men and 33 women. The results of this research revealed that before the Belo Monte hydroelectric plant, the members of the communities investigated used the fishery as the main subsistence craft. Residents of the Mexican community (single resettled) still cultivated plants and vegetables to supplement their livelihoods. With the completion of the dam works, it is possible to verify that there are already changes in the application of the traditional knowledge of these peoples. This is because most of the riverside communities were forced to change their profession, either because they had been resettled in distant localities, but mainly because of the hydroelectric impacts on the biodiversity of fish on the Xingu River. The results of this research, although preliminary, demonstrate the need to create innovative solutions that combine energy production with economic, environmental and social benefits, based mainly on sustainable practices.