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Tropical rainforests provide essential ecosystem services to agricultural areas, including moisture recycling. In the Amazon basin, drought frequency has increased in the late 20th and early 21st centuries, but the role of forests, ocean, and nonforested areas in causing or mitigating drought has not been determined. Using a precipitationshed moisture tracking framework, we quantify the contribution sources of evaporation to rainfall in Rondônia in the Brazilian Amazon. Forests account for ∼48% of annual rainfall on average, and more than half of the forest source is from protected areas (PAs). During droughts in 2005 and 2010, moisture supply decreased from oceans and nonforested areas, while supply from forests was stable and compensated for the decrease. Remote sensing and land surface models corroborate the relative insensitivity of forest evapotranspiration to droughts. Forests mitigate drought in the agricultural study region, providing an important ecosystem service that could be disrupted with further deforestation. Plain Language Summary: Tropical rainforests provide ecosystem services for humanity, including moisture recycling, which refers to moisture that evaporates from a forest, travels through the atmosphere, and returns as precipitation downwind. Drought frequency has increased in parts of the Amazon, but the role of forest ecosystem services in mitigating or exacerbating droughts is not known. We used a climate model to examine the contribution of forest, ocean, and nonforested areas, which include agriculture, to rainfall during normal and drought years in the Brazilian State of Rondônia in the Amazon Ocean sources contributed less during severe droughts, and forests contributed more and mitigated the reduction of rainfall. We conclude that the rainfall in this part of the Amazon is vulnerable to forest loss in other parts of the Amazon, which buffers the magnitude of rainfall reduction during drought events. Key Points: During drought years, ocean sources of precipitation failed while the percent contribution from forests increasedRainfall in a key agricultural region of the Amazon is vulnerable to forest lossForests are important for precipitation for this agricultural region of the Amazon, but forests have varying levels of protection [ABSTRACT FROM AUTHOR]