Previous tree ring based hydrologic studies in Mongolia have been regional in scale. Here, we present a large-scale summer drought reconstruction for Mongolia that reveals the main summer moisture patterns of the past. This reconstruction is based on a network of tree ring chronologies that span the country. The resulting drought model explains 61% of the variance and is extended to cover 1520–1993 by using a nested approach to modeling. Severe droughts and harsh winter conditions occurred in Mongolia from ∼1999–2002 and contributed to massive livestock mortality and economic loss. These droughts were extreme in the context of the past several hundred years. Significant periodicities are found at 40 (90%), 19.3–25 (99%), 11.6 (95%), 6.4–7.2 (95%), and 2.8 years (99%). This high-resolution drought reconstruction and associated tree ring chronologies supplement and extend the sparse meteorological data in Mongolia and can be used to better understand climate variability and potential forcings of climate.