Renewable energy is becoming increasingly popular because it is cheap, cleaner, and more effi-cient than traditional forms of energy. Hydropower is the world's most significant source of renewable energy, and it is commonly regarded as green energy that can be produced in an environmentally beneficial way. The aim of this research is to explore the asymmetric effect of hydropower energy consumption on CO2 emissions in the top ten Hydropower-consumer Euro-pean Union economies (Norway, Sweden, France, Italy, Austria, Switzerland, Spain, Germany, Finland, and Portugal) by using the data from 1991 to 2019. Earlier studies emphasized on panel data techniques to explore the hydropower energy consumption-CO2 emissions association, dis-regarding the reality that many economies lack evidence of such a link on their own. In contrast, this study utilizes a unique approach "Quantile-on-Quantile" that assesses the time-series de-pendency for each economy independently to acquire worldwide but nation-specific knowledge on the asymmetric connection between the variables. Hydropower usage, according to estimates, significantly reduces CO2 emissions at various quantiles in all our sample nations except Portugal. The levels of asymmetry in the hydropower-CO2 emissions association, on the other hand, differ by nation, requiring extra care and government vigilance when designing hydropower and sus-tainable environmental strategies. This research advocates strengthening the role of hydropower dynamics in minimizing CO2 emissions in European Union economies.