Here we analyze the effects that climatic changes through last ice age had on the potential distributions and extinction risk dynamics of two extinct species of South American giant ground sloths, Eremotherium laurillardi and Megatherium americanum. We tested the assumption of stability of the climate preferences through time for the two species and modeled their potential distributions at last glacial maximum (LGM, 21 ky BP) and mid-Holocene (6 ky BP) using Bioclimatic Envelope Modeling (BEM), fossil records and paleoclimatic simulations. The model predictions showed a drastic reduction of the geographical ranges for both species during mid-Holocene, along with a considerable fragmentation of their core climatic conditions and refugia, although it did not fully disappear at this time. Thus, our findings point out that the extinction risk of both species greatly increased as a consequence of the climate change, although do not support it as the unique stressor.