The climatic, hydrographic, and environmental regimes of terminal Pleistocene and Holocene northwestern Mongolia are reconstructed using archaeological and pedological data sets at Bayan Nuur, a lake on the northwestern perimeter of the Altan Els dune field in eastern Uvs Province, Mongolia. The archaeological data consist of land-use patterns controlled for time via time-sensitive, diagnostic artifacts. The pedological data consist of soil classifications and radiocarbon dating of paleosols that track lake levels and water table. These data are combined using a geographic information system (GIS) to ascertain site and paleosol geographic relationships to modern lake levels at Bayan Nuur. They point to a more xeric Younger Dryas than previously recognized, significant Holocene lake regressions, and to Mid- to Late Holocene lake standstills/transgressions, the scale of which had previously been unrecognized. Combined, these data point to a complex late Quaternary picture of paleoclimate and paleoenvironment across the region and the importance of using multiple proxies, including archaeological data, in paleoecological reconstructions.