Study region: Nile River basin (NRB), Northeastern Africa. Study focus: Despite substantial recent vegetation changes in the NRB, their influence on local temperature and precipitation remains uncertain, limiting effective climate adaptation, land management, and water-resource planning in this region. This study examines how vegetation dynamics affect regional climate and the biogeophysical mechanisms driving vegetation-climate feedbacks from 1982 to 2020 using the Community Earth System Model version 2 (CESM2), combined with long-term remote sensing data and a regression model capturing bidirectional interactions between leaf area index (LAI) and climate variables. New hydrological insights for the region: About 54 % of the basin's vegetated areas show significant increases in LAI. In most regions, enhanced vegetation density exerts a cooling effect through increased evapotranspiration, reducing temperature across 43 % of vegetated land, particularly in forest- and shrub-dominated areas. However, in high-elevation regions of Ethiopia, Kenya, and Uganda, vegetation induced surface warming effect by reducing albedo and enhancing solar energy absorption. Overall, vegetation change contributes to a net basin cooling of 0.02 +/- 0.006 degrees C per decade, offsetting 9.5 +/- 2.9 % of NRB warming over 39 years. Impacts on precipitation are weak and spatially inconsistent, with only semi-arid regions showing slight positive feedback. Seasonal variability is strong, evapotranspiration-driven cooling and positive precipitation responses dominate June-September and October-January, whereas radiative warming and negative precipitation responses prevail from February-May. Non-radiative processes are the primary drivers of climate responses to vegetation change. These findings highlight the importance of incorporating vegetation dynamics into climate mitigation, adaptation strategies, and model refinement.