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Land use and climate change are expected to significantly alter hydrology and consequently electricity production in countries extremely dependent on their water resources, such as Brazil. Therefore, we used the large-scale hydrological model Soil and Water Assessment Tool (SWAT), which we integrated with climate change and land use scenarios for the Tocantins-Araguaia Watershed (TAW) with a focus on energy production at the Tucuruí Hydroelectric Plant (THP) in the southeastern Amazon. We used daily precipitation and temperature data from two General Circulation Models (GCM), HadGEM2-ES and MIROC5 with moderate (+4.5 W/m2 in the year 2100 relative to pre-industrial levels) and severe (+8.5 W/m2) radiative forcing from carbon dioxide emissions in the atmosphere (Representative Concentration Pathways). For the land use and land cover change (LULCC) scenario, we replaced forest areas only with pasture, then with agriculture, then with reforestation vegetation, and finally with regenerated forest. Each LULCC period was coupled with the highest impact climate scenario found for TAW (MIROC5-RCP 8.5); thus, we investigated five scenarios and their impacts on hydropower production and revenue in THP. Our results highlight that the TAW will face a large water reduction by the end of the century, which in all scenarios will strongly impact the basin’s energy production and hydro revenue. Reductions of up to 74% in annual flow and 63% in electricity generation are expected for the most pessimistic scenario (L8.5), triggering a 135% deficit per year in THP revenue. Although some land use change scenarios partially minimize the climate-driven flow decrease trend in the period of higher precipitation, there is still a dramatic reduction in flow during the dry season, thus exacerbating seasonal and inter-annual variability.