Hydropower is the most important renewable energy source for electricity in Norway. However, it is the most vulnerable resource to climate change. Despite the importance of hydropower and its vulnerability to climate change, many studies have been mostly concerned with large-scale resources assessment. This study aims to address the climate change impacts on the scale of a single hydropower system in Norway. The impact studies are based on a combination of hydrological model and a hydropower simulation model driven by scenarios from the Atmospheric-Ocean General Circulation Model (AOGCM). These climate scenarios were used for driving the HBV (Hydrologiska Byråns Vattenbalansavdelning) hydrological model to provide inflow scenarios for the hydropower study. The nMAG hydropower simulation model was used to simulate the hydropower system for the control and scenario period and to investigate future changes in power production. In general, the projections indicate an average increase of 11–17% in annual inflow to the system, earlier peaks and a larger increase in spring. The hydropower simulation results show an increase in energy generation of 9–20% under the current reservoir operation strategies.