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An important role of the South American Monsoon System (SAMS) is in driving the water balance in the tropics and subtropics by modulating the Tropical Atlantic Ocean’s moisture flux that enters South America at its northern coast and is deviated southwardly by the Andes to end up contributing to subtropical precipitation. An yet open question is how this picture might be changed under the upcoming anthropogenic climate changes. We draw some light on the matter by comparing modeled moisture fluxes for the 20th and 21th centuries. The Brazilian Model of the Global Climate System (BMGCS), which is being developed by the Brazilian scientific community for its climate change studies and is known to reproduce the SAMS, is used for this study. Sea surface temperature (SST) fields from Hadley Center-HadCM3, GFDL-CM2.1 and MPI-ECHAM5 models produced on the 20C3M, A2 and B1 experiments are used to force the atmospheric component of BMGCS and downscale these IPCC scenarios. The vertically integrated moisture flux and the moisture balance over South America is analyzed here for each of our nine model integrations. Our results for the rainy season (NDJFM) season shows an intensification of the moisture flux crossing the continent, which is more strong under A2 scenario than under B1. This is in agreement with many studies that shown an intensification of the global hydrological cycle for a warmer climate and particularly those that points to increased precipitation in subtropical South America.