East Antarctica has shown little evidence of warming to date1–3 with no coherent picture of how climate change is affecting vegetation4–6. In stark contrast, the Antarctic Peninsula experienced some of the most rapid warming on the planet at the end of the last century2,3,7,8 causing changes to the growth and distribution of plants9–11. Here, we show that vegetation in the Windmill Islands, East Antarctica is changing rapidly in response to a drying climate. This drying trend is evident across the region, as demonstrated by changes in isotopic signatures measured along moss shoots12,13, moss community composition and declining health, as well as long-term observations of lake salinity14 and weather. The regional drying is possibly due to the more positive Southern Annular Mode in recent decades. The more positive Southern Annular Mode is a consequence of Antarctic ozone depletion and increased greenhouse gases, and causes strong westerly winds to circulate closer to the continent, maintaining colder temperatures in East Antarctica despite the increasing global average15–18. Colder summers in this region probably result in reduced snow melt and increased aridity. We demonstrate that rapid vegetation change is occurring in East Antarctica and that its mosses provide potentially important proxies for monitoring coastal climate change.