These days land use land cover change is the global concern. This is very crucial issue in Ethiopia where there is high population growth. This study was done in northern Ethiopia (Tirari watershed, Tekeze basin) where there is high land degradation due to long years of extensive farming and population pressure. The main objective of this study was determining effect of land use the land cover change on streamflow on the watershed. Satellite images from TM, ETM+ and OLI/TIRS data were classified by supervised classification technique using maximum likelihood algorithm and the classified images were checked for its classification accuracy. The classified images were analysed for land use land cover change analysis and change detection in the watershed. SWAT model was used to determine the effect of land use land cover change on the response of the watershed. The SWAT CUP was used for calibration and validation of SWAT outputs. The result of the study area covered with in different study years increase bare land, cultivated land and also decrease forest area respectively. The results showed that the streamflow changes due to the change in land use land cover in the Tirari watershed, the monthly streamflow was increased by 5.03% (2000-2010), decrease by 13%(2010-2020) and also total study years decrease by 7.97%(2000_2020). The performance of the model result was a good relation between observed and simulated data by different criteria during calibration period R 2 =0.72 and ENS =0.71 and validation period R 2 =0.71 and ENS=0.65. By varying the amount of surface runoff in the study period (2000-2010) wet season increase (9%) and dry season decrease by 1.14% ,(2010_2020) wet season decrease (30%), and dry season decrease (6%) and total year variation from 2000 to 2020 wet season decrease by (21.1%) and dry season decrease by (7.22%). The flow was increased, while intense rainfall and decrease infiltration, these results due to incremental of bare land and cultivated land and decrement forest area in the study year. When this impact could be minimized by the development of future mitigation, conservation, and adaptation measures of land use land cover in the study area. By conservation and re-habitation of the watershed, we can sustain and increase the base flow of the river to get the best possible water for irrigation schemes in the watershed outlet. Keyword: Geographic Information system (GIS), Tirari Watershed, Land use land cover change (LULCC), Soil and Water Assessment Tool (SWAT), Remote sensing (RS), Streamflow