There are current studies which are indicating climate change is affecting the availability of water resources. In order to evaluate the future impacts of climate change on the extreme hydrology, this study was carried out in three watersheds (GilgelAbbay, Temcha, and Anjeni) of the upper Blue Nile. The study used the new emission scenarios Representative concentration pathway (RCP) based on IPCC fifth assessment report (AR5) with 50km resolution. The GCM (Global Circulation Model) output of RCP 2.6 and RCP 8.5 emission scenarios were used. The Parameter Efficient semi Distributed Water Balance model (PED-WM) was calibrated and validated to project the climate change impacts on the extreme stream flow. The future climate projection result were presented by dividing in to three future time horizons of 2030s (2021-2040), 2060s (2051-2070) and 2090s (2081-2100). The bias corrected GCM projection indicated that, maximum and minimum temperature increases in all months and seasons in the selected watersheds. The change in magnitude in RCP 8.5 emission was higher than RCP 2.6 scenario. The study resulted considerable average monthly, seasonal and annual precipitation change variability in magnitude and direction. Based on this study Stream flow is expected to decrease in the projection period. In 2030s, the average annual Stream flow projection decreases up to -32.18% for RCP 2.6 and up to-19.44% for RCP 8.5 scenarios. In 2060s also the average annual Stream flow decreases by -12.3% and 32.18% for RCP 2.6 and RCP 8.5 emission scenarios, respectively. Similarly, in 2090s, the average annual Stream flow change decreases by -20.67 and -51.78% for RCP2.6 and RCP8.5 respectively. For the future time horizon, the maximum Stream flow changes in wide range from (-56.4 to 81.1%) and minimum flow from (-61.72 to 8.17%) in both RCP2.6 and RCP8.5. Hence, the decrements of Stream flow volume in the watersheds would have a significant impact for the sustainability of existed and undergoing water development projects. Due to this a precaution of mitigation and adaptation measures ought to be developed for possible droughts in the area of the River basin.