The exact extent, by which the hydrologic cycle in the Neotropics was affected by external forcing during the last deglaciation, remains poorly understood. Here we present a new paleo-rainfall reconstruction based on high-resolution speleothem δ18O records from the core region of the South American Monsoon System (SAMS), documenting the changing hydrological conditions over tropical South America (SA), in particular during abrupt millennial-scale events. This new record provides the best-resolved and most accurately constrained geochronology of any proxy from South America for this time period, spanning from the Last Glacial Maximum (LGM) to the mid-Holocene.