More than 20% of the Amazon rainforest has been cleared in the past three decades1, triggering important hydroclimatic changes1, 2, 3, 4, 5, 6. Small-scale (a few kilometres) deforestation in the 1980s has caused thermally triggered atmospheric circulations7 that increase regional cloudiness8, 9, 10 and precipitation frequency8. However, these circulations are predicted to diminish as deforestation increases11, 12, 13. Here we use multi-decadal satellite records14, 15 and numerical model simulations to show a regime shift in the regional hydroclimate accompanying increasing deforestation in Rondônia, Brazil. Compared with the 1980s, present-day deforested areas in downwind western Rondônia are found to be wetter than upwind eastern deforested areas during the local dry season. The resultant precipitation change in the two regions is approximately ±25% of the deforested area mean. Meso-resolution simulations robustly reproduce this transition when forced with increasing deforestation alone, showing that large-scale climate variability plays a negligible role16. Furthermore, deforestation-induced surface roughness reduction is found to play an essential role in the present-day dry-season hydroclimate. Our study illustrates the strong scale sensitivity of the climatic response to Amazonian deforestation and suggests that deforestation is sufficiently advanced to have caused a shift from a thermally to a dynamically driven hydroclimatic regime.