Abstract. Evapotranspiration (ET) is one of the least understood components of the hydrological cycle. Its application is varied, from agricultural, ecological and hydrological monitoring, to control of the evolution of climate change. The goal of this work was to analyze the influence that uncertainties in the estimate of Land Surface Temperature (LST) can cause on ET estimates by S-SEBI model in Pampa Biome area. The results indicate that the daily evapotranspiration is higher when the pixel LST is lower, which also shows the influence of land use on the variability of ET. They also demonstrated the importance of LST's accuracy in the selection of the driest and wettest pixels in applying S-SEBI model, because when there are uncertainties in estimates of LST, the errors in the estimates of the energy components multiply. The Pampa Biome native grass crops have lower Latent Heat Flux (LET) than other land uses, with higher values of LET during the spring-summer period when compared to autumn-winter.