Ethiopia considered to have abundant water resources potential is facing flood and drought possibly from poor water resource management and reluctant policy. Awash river basin classified in to upper, middle, and lower crosses Ethiopian plateau through the Afar desert. Among the basin classes, the upper basin is socio-economically important wherein the early and modern agriculture start is the most irrigated basin. Addis Ababa the capital and different major towns are getting their domestic Water supply from this basin. The study aimed to assess the basin’s hydroclimate variability under the climate change during study time series. Basin’s Metrological trend is analyzed with systematic topographical classes as Lowland, midland, and highland. Lowland (Mojo and Bishoftu station) revealed nonsignificant increasing trend except for the Bona and Birraa season respectively. Midland area stations revealed a seasonal decrease with precipitation except Asgori station is increasing in the Birraa season. Highland area stations exhibited a decreasing trend annually and in Arfaasaa seasons except Sendafa station got an increasing trend. Addis Alem station decreased Annually at a 95% significance level while other are statistically insignificant. The streamflow of the basin evaluated with Awash-Hombole and Mojo main tributary river flow. Awash-Hombole main tributaries resulted in increasing trend annually and during Ganna season. Berga, Holota, Melka-Kunture and Hombole stations are insignificantly increasing annually. Mojo main tributary resulted in a significant decreasing trend during the Arfaasaa, Ganna and Birraa season at 99% significant level. Basin streamflow change within the study time series is observed within the model’s observation confidence interval of 95% except for the 1996 steam flow. Therefore, there is change observed within the basing both with rainfall and streamflow according to basin’s topographic nature. Thus, the basin’s hydroclimate variated by 11.38% and 38.19% rainfall and streamflow respectively from the mean value within the study time series.