The expansion of the Brazilian electricity sector is based on the construction of new dams. However, dams generate impacts, especially on riverine communities. Thus, this paper examined the local communities perceptions about the socioeconomic and environmental impacts of the Santo Antônio do Jari Dam, in Amapá. Data were obtained through surveys using the snowball sampling method. To analyze the perception data the Bardin’s analysis of content was used. The research showed that, before the construction of the dam, there was a very intimate bond between the communities, the environment and the nature, which influenced the communities perceptions mainly regarding environmental impacts, relocation, changes in livelihood and access to natural resources.