Climate variability and land use change are major factors that affect watershed hydrology regionally and globally. This study aims to determine the effects of climate variability and land use change in the Gilgel Abay watershed. The determination of the trend and change point in hydroclimatic data is important for a better understanding of the effects on watershed hydrology. The trends in precipitation, streamflow, and potential evapotranspiration were examined through Mann-Kendall and Innovative trend detection approach. In addition, changepoints were detected through Pettitt’s test. For attribution analysis of the effects, the hydroclimatic data was divided into two time periods: the baseline (1990-2001) and the altered period (2002-2016). The Pettitt test detects change point in streamflow data between (1990-2016), with 2001 serving as a change year. The results of the trend analysis show a significant decrease in stream flow and an increase in potential evapotranspiration, while insignificant trend in precipitation. From the hydrological modeling, climate elasticity, hydrological sensitivity, linear regression, and multiple linear regression approaches; the relative anthropogenic disturbances and climate variability were 93.9 (6.1) %, 92.5(7.5) %, 73 (27) %, 58(42) %, and 51(49) % on the changes in stream flow on the Gilgel Abay watershed, respectively. The relative contribution of anthropogenic disturbance on average (73.48%) is greater than that of climate variability (26.32%) on stream flow change in the watershed. Therefore, to reduce the impact of anthropogenic land use change on the hydrological processes of the Gilgel Abay watershed, appropriate integrated watershed management strategies should be implemented. The findings of this study will help in understanding how anthropogenic land use change and climate variability affect water resources at both small-scale and large-scale catchment studies. Keywords: Climatic variability, land use change, Water resources, Gilgel Abay watershed, Ethiopia