Abstract Despite extensive discussion in the literature about the socio-economic impacts of hydropower development on surrounding communities, there is (1) a lack of quantitative studies that look at impacts over extended periods of time and (2) a lack of studies including multiple projects in the context of a developing country. Here, we use econometric methods to evaluate the relationship between county-level socio-economic indicators and hydropower development for 56 Brazilian hydropower plants built between 1991 and 2010. We find that counties that built hydropower plants had greater GDP and tax revenues during their first few years of development than a control group that consisted of counties with hydropower projects planned but not yet built. However, those positive economic effects were short lived (