This study aims to evaluate the hydropower potential of irrigation reservoirs throughout Japan, using a neural network model to estimate the flow regime and calculate the hydropower generation. The results showed that reservoirs throughout Japan have the potential to generate between 14 GWh/year and 63 GWh/year of electricity. The annual hydropower generation potential of irrigation reservoirs, estimated according to the flow regime of eight large agricultural irrigation dams, was found to range from 44 GWh/year to 180 GWh/year. In addition, the results show high hydropower potential in Kochi, Hyogo, Kagoshima, Miyazaki and Oita prefectures, with the maximum estimated hydropower generation of 16 GWh/year, 8 GWh/year, 4 GWh/year, 4 GWh/year and 3 GWh/year, respectively.