Evapotranspiration (ET) is a key factor in the water and energy cycle, playing a critical role, especially in agricultural regions. The eastern German lowlands, with their continental climate, are one of the driest regions in Germany, yet agriculture is the dominant land use. This study investigates the spatio-temporal variability of ET and its response to climate and land use/land cover change (LUCC) using MODIS remote sensing products and in-situ measurements over the period 2000-2020. The results show a slight increase in the mean annual ET, with local increases of up to 7.2% in the southern and southeastern parts of Brandenburg. LUCC revealed a 22.2% decrease in grassland to cropland conversion, leading to a decline in ET of 21%, while conversion from grassland to cropland increased by 14.8%, resulting in a 10% increase in ET. The strongest relationship with ET was found for vapor pressure deficit (VPD), temperature (Temp), and relative humidity (RH), which contributed 25.2%, 30.9%, and 23.2%, respectively, to its total variability. In addition to atmospheric factors soil moisture (SM) also contributed 17.7% to ET, but only in grassland. LUCC played a minor role as 22% of the study area was under conversion. Consequently, climate change, represented by the temporal change of the climatic factors, was identified as the dominant driver of ET in the study area, accounting for 97% of its variability. Accordingly, these findings underscore the importance of Temp, RH, and SM in agricultural and water resource management.