The global climate may have serious impact on the frequency, magnitude, location and durations ofrnhydrological extremes. Change in hydrological extremes will have implications on the design ofrnfuture hydraulic structures, flood- plain development and water resource management .This studyrnassesses the potential impact of climate change on extreme hydrological events in Akaki Riverrncatchment in and around Addis Ababa area. Projection of the future climate variables is done byrnusing General Circulation Model (GCM) which is considered as the most advanced tool forrnestimating the future climatic condition. The climate projection analysis was done by dividing therncoming 90 years into two time periods. The 1990-1999 was taken as baseline period against whichrncomparison was made. A hydrological model, HEC-HMS was utilized to simulate Runoff in thernstudy area. The performance of the model was assessed through calibration and validation processrnand resulted R2=0.78 during calibration and R2=0.81 during validation.rnFor the coming 90 years, the mean monthly precipitation may both increase and decrease. Therndecrease in mean monthly precipitation may be up to 51% in 2030s and the increase may reach uprnto 131% in 2090s. The maximum and minimum temperature indicated an increasing trend. Thernsimulated result shows that the maximum river flows in the study area will be high and more variablernin terms of magnitude, and irregular of occurrence, than they are at present. It is observed thatrnclimate change has negligible effect on the low flow condition of the Akaki River flow. Accordingrnto the evaluated scenarios, climate change has impact on the distributions of hydrological extremes inrnthe study area. The impact of climate change may also cause a decrease in monthly mean flow up torn41% in the 2030s and increase up to 126% in the 2090s. Seasonal mean flow may show increase uprnto 13% and 15% in Kiremt (JJAS) season for 2030s and 2090s time periods respectively. Thernincreasing of seasonal mean flow in Kermit (JJAS) has its own contribution for occurrence ofrnflooding in Addis Ababa city. The increase in Bega (ONDJ) season flow will have a paramountrnimportance for water harvesting in dam of water supply to Addis Ababa city. It is observed thatrnthere may be a net annual increase in mean annual flow volume in Akaki River due to climaternchange.rnKey words: Climate change; GCM, SDSM, flood; low flow; HEC-HMS; Addis Ababa