This work aimed to assess reference evapotranspiration (ET0) trends and its sensitivity to climate variables on the period 2036–2065 in the Senegal River basin. Seven General Circulation Models (GCMs) and seven Regional Climate Models (RCMs) of the CMIP5 project were used under the scenarios RCP4.5 and RCP8.5. The performance of GCMs and RCMs was first evaluated by comparing their outputs with the reanalyses data. The change of ET0 is determined between the periods 1971–2000 and 2036–2065. A sensitivity coefficient was calculated to analyze the influence of climatic variables on ET0. Finally, the Mann Kendall test and Sen slope were used to detect future trends in ET0 and climate variables. New hydrological insights for the region It was found that RCMs were here more robust than GCMs in estimating reference evapotranspiration over the period 1984–2000. Compared to the period 1971–2000, the RCMs show that ET0 will increase by 14–293 mm under RCP4.5 and by 55–387 mm under RCP8.5 according to the climatic zones. The maximum values are observed in Sahelian zone and the minimum one in Guinean area. The sensitivity analysis shows that ET0 is more sensitive to relative humidity, maximum temperature and solar radiation. The trend analysis reveals, generally, a significant increase in ET0 and in maximum and minimum temperatures in the period 2036–2065 under the RCP4.5 and RCP8.5 scenarios. This means that ET0 will not be stationary and may continue to increase after 2065 because of the increase of temperature.