Domesticated yaks endure as iconic symbols of high-altitude frozen landscapes, where herding communities depend on their high-fat milk, transport, dung, and natural fibers. While there is established proteomic evidence for ancient consumption of ruminant and horse milk in the mountains and steppes of northern Eurasia, yak dairy products have yet to be detected. Yak domestication and the species’ dispersal from Tibet into the mountainous zones to the north are also poorly resolved due to a paucity of zooarchaeological data. To examine the potential of paleoproteomics to shed light on domesticated yak in Mongolia, we analyzed human dental calculus from Mongol era elite individuals recovered from permafrost burials in Khovsgol province, where people continue to herd yak to this day. We report the first evidence for yak dairy consumption, linked to local resource control. In addition, we confirm a large diversity of recovered whey, curd, tissue, and blood proteins, likely reflecting the excellent preservation conditions found at permafrost sites.