Understanding the impacts of land use land cover (LULC) changes on hydrology, ecosystem functions and services is indispensable not only to identify challenges and targeting interventions but also for watershed management planning measures. However, there is no comprehensive study on the impacts of LULC changes on hydrology, ecosystem functions and services with respect to the past and future periods in the Upper Blue Nile basin of Ethiopia. This study was intended to comprehend the impacts of LULC changes on hydrology, soil erosion, sediment yield and ecosystem services in the Andassa watershed of the Upper Blue Nile basin during the 1985- 2015 periods, and predict its impact in the coming three decades of the period from 2015 to 2045. The hybrid land use classification technique for classifying time series Landsat images (1985, 2000 and 2015); the Cellular-Automata Markov (CA-Markov) model for prediction of the 2030 and 2045 LULC states; the Soil and Water Assessment Tool (SWAT) for hydrological modeling; the Revised Universal Soil Loss Equation (RUSLE) model for estimating the rate of soil erosion; the Sediment Delivery Distributed (SEDD) model for sediment yield modeling; the modified ecosystem services valuation model for exploring the changes in ecosystem services were employed. The different layers of the spatiotemporal changes on the LULC were the basis for examining the changes in hydrology, soil erosion, sediment yield and ecosystem services. The results showed that in the past three decades, cultivated land and built-up areas significantly increased while areas occupied by natural vegetation such as forest land, shrublands and grasslands dwindled at a rapid rate. The predicted results suggest a continuation of the trend unless management interventions are made today. The LULC changes, which had occurred during the period of 1985 to 2015, had increased the annual flow (2.2%), wet seasonal flow (4.6%), surface runoff (9.3%) and water yield (2.4%). Conversely, the observed changes had reduced the dry season flow (2.8%), lateral flow (5.7%), groundwater flow (7.8%) and ET (0.3%). The 2030 and 2045 LULC states are expected to further increase the annual and wet season flow, surface runoff and water yield, and reduce the dry season flow, groundwater flow, iii lateral flow and ET. The LULC changes have also increased the annual soil erosion rate from 35.5 t ha-1 yr-1 in 1985 to 55 t ha-1 yr-1 in 2015, and sediment yield from 14.8 t ha-1 yr-1 in 1985 to 22.1 t ha-1 yr-1 in 2015. The prediction result also shows that the increases in soil erosion and sediment yield are expected to continue in the 2030 and 2045 periods. The LULC changes occurred between 1985-2015 periods has also reduced most of the provisioning, regulating, supporting and cultural services. If the LULC changes are continued as a usual case business scenario, most of the services are expected to reduce between 2015-2045 periods. The change in hydrological components, soil erosion, sediment yield and ecosystem services are a direct result of the significant transition from the vegetation to non-vegetation cover in the watershed. These suggest an urgent need to regulate the LULC changes in order to maintain the hydrological balance, to arrest the expected increase of soil erosion and sediment yield, and to reduce the expected loss of ecosystem services.