Land use change is one of the main driving factors of hydrological change in watersheds. Therefore, hydrological responses to land use changes require detailed assessments to ensure sustainable management of both water resources and natural ecosystems. The objective of this study was to simulate the impact of different land use change scenarios (LULC: 1985, 1995, 2005 and 2015) on the water balance, through the hydrological model Soil and Water Assessment Tool (SWAT), in the Puyango Tumbes river basin belonging to Ecuador and Peru during a period of 35 years (1981 - 2015). The LULC analysis shows that there was an increase in the percentage of watershed area covered by grasslands by 18 % while there was a decrease in savannahs by 38 %. In addition, the characteristics of the flow changed from 1985 to 2015 considering their corresponding LULC in the three hydrometric stations analyzed for the period 1981 - 2015. Thus, decreases in annual flows were estimated in that period for the Pindo station (Ecuador) in 4 m 3/s, the Puyango station (Ecuador) at 29 m3/s and the El Tigre station (Peru) with 16.48 m3/s. The dynamics of the hydrological cycle throughout the basin presented (1981 - 2015) an increasing trend in evapotranspiration with 2.14 % and, on the contrary, a decrease in surface flow by 20.7 %, percolation by 29.29% and lateral flow by 0.93 %. The evidence of these changes and the evaluation of their effects are particularly relevant for the long-term sustainable management of water resources and especially as it is a binational basin